The board of education of any city, exempted village, or local school district may establish and maintain part-time schools or classes for the further education of children who are employed on age and schooling certificates. Such schools and classes shall be conducted not fewer than four hours per week while in session, and for not fewer than one hundred forty-four hours per calendar year between the hours of seven in the morning and six in the afternoon, excluding Saturday afternoon and Sunday. Such schools and classes shall be conducted under such standards as the state board of education prescribes. Boards of education may provide for the expense of such schools and classes the same as for the expense of ordinary elementary schools.