1. On and after the effective date of sections 169.010 to 169.140, all employees as defined in sections 169.010 to 169.141 of districts included in the retirement system thereby created shall be members of the system by virtue of their employment, except as provided by section 104.342. Individuals who qualify as independent contractors under the common law and are treated as such by their employer shall not be considered employees for purposes of membership in or contributions to the retirement system.

2. Any person who becomes a member before the end of the school year next following the date on which the system becomes operative may claim credit for service rendered as an employee in Missouri prior to such operative date, or for service rendered in the Armed Forces of the United States during a period of war, the same as if the person were a teacher, provided the person was a teacher in Missouri at the time the person was inducted, by filing with the board of trustees, within such time as the board may specify, a complete and detailed record of the service for which credit is claimed, together with such supporting evidence as the board may require for verification of the record. To the extent that the board finds the record correct, it shall credit the claimant with prior service and shall notify the claimant of its decision, but the amount of such credit shall not exceed thirty years.

3. No prior service credit shall be granted to any person who becomes a member after the first year of the system’s operation, except as provided in subsection 5 of this section unless that person’s failure to become a member before or during that year was due either to service in the Armed Forces of the United States or to attendance at a recognized educational institution for professional improvement; provided, that the board of trustees may grant prior service credit to a teacher who taught prior to August 1, 1945, if the teacher returns to teaching before July 1, 1950, and if such teacher teaches in the public schools of Missouri not less than seven years after returning before retirement, or the board of trustees may grant prior service credit to a teacher who taught prior to August 1, 1945, if the teacher returns to teaching and teaches at least one-half of the number of years between July 1, 1946, and age sixty but not less than seven years after returning before retirement, except that a member who will have thirty-five or more years of teaching service in Missouri at retirement shall be required to teach not less than three years after returning and before retirement. A person serving in the Armed Forces of the United States shall have the same right to prior service credit as one who became a member before the end of the first year of the system’s operation, if the person becomes a member within one year of the date of the person’s discharge from such service or within one year of such date plus time spent as a student in a standard college or university in further preparation for service as a public school employee. A person attending a recognized educational institution for the person’s professional improvement shall have the same right to prior service credit as one who became a member before the end of the first year of the system’s operation, if the person becomes a member within three years following the date on which the system became operative, and within one year of the date on which the person’s attendance at such institution ceased.

4. Membership shall be terminated by failure of a member to earn any membership credit as a public school employee under this system for five consecutive school years, by death, withdrawal of contributions, or retirement.

5. If a member withdraws or is refunded the member’s contributions, the member shall thereby forfeit any creditable service the member may have; provided, however, if such person again becomes a member of the system, the person may elect to reinstate the creditable service forfeited at times of previous withdrawals or refunds. The reinstatement shall be effected by the member paying to the retirement system with interest the total amount of accumulated contributions withdrawn by the member or refunded to the member with respect to the service being reinstated. A member may reinstate less than the total service previously forfeited, in accordance with rules promulgated by the board of trustees. The payment shall be completed prior to termination of membership with the retirement system with interest on the unpaid balance; provided, however, that if a member is retired on disability before completing such payments, the balance due with interest may be deducted from the member’s disability retirement allowance.