Regularly certified and appointed teachers who desire to have the following described services credited for pension purposes shall submit to the Board evidence thereof and pay into the Fund the amounts prescribed herein:
For each year of service credit to be established under this subparagraph 6, a member is required to contribute to the System (i) the employee and employer contribution that would have been required had such service been rendered as a member based on the annual salary rate during the first year of full-time employment as a teacher under this Article following the private school service, plus (ii) interest thereon at the actuarially assumed rate from the date of first full-time employment as a teacher under this Article following the private school service to the date of payment, compounded annually. For service described in sub-paragraphs 1, 2 and 3 of this Section, interest shall be charged beginning one year after the effective date of appointment or reappointment.
Effective September 1, 1974, the interest rate to be charged by the Fund on contributions provided in sub-paragraphs 1, 2, 3 and 4 shall be 5% per annum compounded annually.
40 ILCS 5/17-133