(a) Whenever used in this section or in sections 10-153c to 10-153n, inclusive: (1) The “administrators’ unit” means the professional employee or employees in a school district or charter school not excluded from the purview of sections 10-153a to 10-153n, inclusive, employed in positions requiring an intermediate administrator or supervisor certificate, or the equivalent thereof, or charter school educator permit, issued by the State Board of Education under the provisions of § 10-145q, and whose administrative or supervisory duties, for purposes of determining membership in the administrators’ unit, shall equal at least fifty per cent of the assigned time of such employee. Certified professional employees covered by the terms and conditions of a contract in effect prior to October 1, 1983, shall continue to be covered by such contract or any successor contract until such time as the employee is covered by the terms and conditions of a contract negotiated by the exclusive bargaining unit of which the employee is a member for purposes of collective bargaining pursuant to the provisions of this section. (2) The “teachers’ unit” means (A) the group of professional employees who hold a certificate or durational shortage area permit issued by the State Board of Education under the provisions of sections 10-144o to 10-149, inclusive, and are employed by a local or regional board of education in positions requiring such a certificate or durational shortage area permit and are not included in the administrators’ unit or excluded from the purview of sections 10-153a to 10-153n, inclusive, and (B) the group of professional employees who hold a certificate, durational shortage area permit issued by the State Board of Education under the provisions of sections 10-144o to 10-149, inclusive, or a charter school educator permit issued by the State Board of Education under the provisions of § 10-145q, and are employed by a charter school in positions requiring such a certificate, durational shortage area permit or charter school educator permit and are not included in the administrators’ unit or excluded from the purview of sections 10-153a to 10-153n, inclusive. (3) “Commissioner” means the Commissioner of Education. (4) “To post a notice” means to post a copy of the indicated material on each bulletin board for teachers in every school in the school district or, if there are no such bulletin boards, to give a copy of such information to each employee in the unit affected by such notice. (5) “Budget submission date” means the date on which a school district is to submit its itemized estimate of the cost of maintenance of public schools for the next following year to the board of finance in each town having a board of finance, to the board of selectmen in each town having no board of finance and, in any city having a board of finance, to said board, and otherwise to the authority making appropriations therein. (6) “Days” means calendar days.

(b) The superintendent of schools, assistant superintendents, certified professional employees who act for the board of education in negotiations with certified professional personnel or are directly responsible to the board of education for personnel relations or budget preparation, temporary substitutes and all noncertified employees of the board of education are excluded from the purview of this section and sections 10-153c to 10-153n, inclusive.

(c) The employees in either unit defined in this section may designate any organization of certified professional employees to represent them in negotiations with respect to salaries, hours and other conditions of employment with the local or regional board of education which employs them by filing, during the period between March first and March thirty-first of any school year, with the board of education a petition which requests recognition of such organization for purposes of negotiation under this section and sections 10-153c to 10-153n, inclusive, and is signed by a majority of the employees in such unit. Where a new school district is formed as the result of the creation of a regional school district, a petition for designation shall also be considered timely if it is filed at any time from the date when such regional school district is approved pursuant to § 10-45 through the first school year of operation of any such school district. Where a new school district is formed as a result of the dissolution of a regional school district, a petition for designation shall also be considered timely if it is filed at any time from the date of the election of a board of education for such school district through the first year of operation of any such school district. Within three school days next following the receipt of such petition, such board shall post a notice of such request for recognition and mail a copy thereof to the commissioner. Such notice shall state the name of the organization designated by the petitioners, the unit to be represented and the date of receipt of such petition by the board. If no petition which requests a representation election and is signed by twenty per cent of the employees in such unit is filed in accordance with the provisions of subsection (d) of this section, with the commissioner within the thirty days next following the date on which the board of education posts notice of the designation petition, such board shall recognize the designated organization as the exclusive representative of the employees in such unit for a period of one year or until a representation election has been held for such unit pursuant to this section and § 10-153c, whichever occurs later. If a petition complying with the provisions of subsection (d) of this section is filed within such period of thirty days, the local or regional board of education shall not recognize any organization so designated until an election has been held pursuant to said sections to determine which organization shall represent such unit.

(d) Twenty per cent or more of the personnel in an administrators’ unit or teachers’ unit may file during the period between March first and April thirtieth of any school year with the commissioner a petition requesting that a representation election be held to elect an organization to represent such unit. Where a new school district is formed as the result of the creation of a regional school district, a petition for a representation election shall also be considered timely if it is filed at any time from the date when such regional school district is approved pursuant to § 10-45 through the first school year of operation of any such school district. Where a new school district is formed as a result of the dissolution of a regional school district, a petition for a representation election shall also be considered timely if it is filed at any time during the first school year of operation of any such school district. Whenever a multiple-year contract is in effect, a petition requesting that a representation election be held to elect an organization to represent such unit shall be considered timely if it is filed with the commissioner between March first and April thirtieth after two years of a contract have elapsed or is filed between March first and April thirtieth of the calendar year prior to the year of expiration of the collective bargaining contract covering the employees who are the subject of the petition, whichever is sooner. The commissioner shall file notice of such petition with the local or regional board of education on or before the fifth school day following receipt of the petition. The commissioner shall not divulge the names on such petition or any petition filed with the commissioner pursuant to this section to anyone except upon court order. Such notice shall state the name of the petitioning group, the unit for which an election is sought and the date the petition was filed. Within three school days after receipt of such notice, the local or regional board of education shall post a copy of the notice. Any organization interested in representing personnel in such unit may intervene within three school days after the board posts notice of such petition by filing with the commissioner a petition signed by ten per cent of the employees in such unit provided that any employee who signs more than one such petition between March first and April thirtieth in any one school year shall not be deemed to have signed any such petition. The commissioner shall notify the local or regional board on or before the third day following receipt of the intervening petition, and such board shall post notice of the intervening petition within three days following receipt thereof. No intervening petition shall be required from any incumbent organization previously designated by the board or elected and such incumbent organization shall be listed on the ballot if a petition for a representation election is filed. The petitioning organization, the incumbent organization, if any, and any intervening organization may agree on an impartial person or agency to conduct such an election consistent with the other provisions of this section, provided not more than one such election shall be held to elect an organization to represent the employees in such unit in any one school year, except, however, if no organization receives a majority of the vote validly cast, the election shall not be deemed completed and within ten days after the initial election a runoff election shall be held. In the event of a disagreement on the agency to conduct the election, the method shall be determined by the board of arbitration selected in accordance with § 10-153c. The person or agency so selected shall conduct, between twenty and forty-five days after the first petition requesting an election is filed with the commissioner, an election by secret ballot to determine which organization, if any, shall represent such unit, provided if no organization receives a majority of the vote validly cast, such election shall not be deemed completed and a runoff election between the two choices receiving the largest and second largest number of valid votes cast in the election shall be held within ten days after the initial election. The organizations participating in the election and the organizations participating in the runoff election shall share equally in the cost incurred by the impartial person or agency selected to conduct each election. Such person or agency shall immediately report the results of the election or runoff election to the commissioner. Within five days after receipt of the tally of ballots in the election or runoff election, any party to said election or runoff election may file with the commissioner any objection to said election or runoff election. If timely objections are found to be valid and they affected the results of the election or runoff election, the commissioner shall order another election or runoff election, as appropriate, to be conducted within ten days of the commissioner’s decision. If satisfied that the election or runoff election has been conducted properly, the commissioner shall certify that the organization receiving a majority of votes is the exclusive representative of the employees in such unit.

(e) The representative designated or elected in accordance with this section shall, from the date of such designation or election, be the exclusive representative of all the employees in such unit for the purposes of negotiating with respect to salaries, hours and other conditions of employment, provided any certified professional employee or group of such employees shall have the right at any time to present any grievance to such persons as the local or regional board of education shall designate for that purpose. The terms of any existing contract shall not be abrogated by the election or designation of a new representative. During the balance of the term of such contract the board of education and the new representative shall have the duty to negotiate pursuant to § 10-153d concerning a successor agreement. The new representative shall, from the date of designation or election, acquire the rights and powers and shall assume the duties and obligations of the existing contract during the period of its effectiveness.

(f) Any organization which has been designated or elected the exclusive representative of a unit which includes teachers and administrators shall continue to be the exclusive representative of such personnel upon expiration of the salary agreement in effect between such organization and the board of education employing such personnel on July 1, 1969, until or unless employees of such board of education in either of the units defined in this section initiate a petition for designation or election of an organization to represent them in accordance with the procedures set forth in sections 10-153a to 10-153n, inclusive.