In each junior college district in which there shall now or hereafter exist a student union building or student center, there is hereby imposed upon each student in attendance at the college of such district a student union fee for the use and availability of such student union building or student center, the amount of which shall be fixed from time to time by the board of trustees of such district, such fee shall be in addition to all other fees authorized to be imposed by such board of trustees and shall not be subject to any statutory limit which may exist on total fees imposed by such board of trustees. Where such student union building or student center shall have been constructed by a junior college housing commission through the issuance of bonds under this chapter, the proceeds of such student union fees shall be regarded as one of the revenues derived from the operation of the student union building or student center, and such board of trustees and such junior college housing commission are authorized to enter into such agreements as they may see fit with respect to the amounts of such fees and the manner of the collection and disposition thereof. Any such agreement may provide that the fees so fixed shall not be diminished or decreased after the issuance of any such bonds until such bonds shall have been retired.