Subsection (l) of section 4 of chapter 32 of the General Laws, as most recently amended by section 1 of chapter 161 of the acts of 2006, is hereby further amended by inserting after paragraph (p) the following paragraph:-

(p1/2)  Any member of a contributory retirement system who is engaged in a teaching position and holds a certificate issued by the department of education or is exempted from the requirement of certification and who was previously engaged in teaching pupils in any charter  school in the commonwealth may establish credit for such service by depositing in the Annuity Savings Fund of the system of which he is a member a sum equal to the amount which would have been paid into such fund during such period if such position has been compensated at the rate of $2500 per year, plus regular interest to the date of payment.