CHICAGO (CBS)– It’s a big day for Chicago Public School teachers, as voting begins Thursday to ratify their tentative contract.

After last month’s teachers’ strike spanned 11 school days, all 25,000 union members are required to vote with secret ballots.

Teachers can vote throughout the day at several schools and at the Chicago Teachers Union office starting at 7 a.m.

The proposed contract needs a simple majority to be ratified. Voting is expected to extend into Friday.

The contract calls to up teachers’ pay by 16% over five years, ringing the average teachers’ salary to around $100,000 a year.

Class sizes will be capped at 28 students in lower grade levels and 31 students at higher grades.

As for support staff, the number of social workers will increase to 665 by the end of the contract and a nurse will be added to every school.

As for those 11 missed days, CPS students and staff will need to make up five of them starting with the day before Thanksgiving.