Ontario's high school teachers have reached a tentative deal with the Liberal government to extend their contracts past the next provincial election.

The Ontario Secondary School Teachers' Federation is the last central education union to reach such a deal with the government. If all are ratified, it would mean the government does not have to contend with contentious education bargaining leading up to the June 2018 vote.

The contracts were set to expire this August, and the new agreements extend them to August 2019.

The last round of negotiations with the education unions saw support staff and elementary teachers staging work-to-rule campaigns and the government threatening to dock their pay.

Contract extension talks arose as part of discussions with education-sector unions over a court ruling that said the government violated their collective bargaining rights.

Legislation in 2012, known as Bill 115, imposed contracts on teachers that froze some of their wages and limited their ability to strike, so five unions took the government to court. The judge sided with them, but left the question of a remedy up to the government and unions to decide.

The OSSTF also said Thursday that it reached a remedy with the government, but wouldn't make details public until its members voted to ratify.

The extensions are all contingent on amendments to the bargaining legislation. Education Minister Mitzie Hunter tabled them this week, and the amendments also include five days of notice required for strikes and lockouts -- that's in addition to five days' notice already required for any job action.

Ontario's French teachers and education workers represented by the Canadian Union of Public Employees have ratified their two-year contract extensions, with English Catholic teachers, elementary teachers and other support workers still to vote on their tentative deals.

Details of various contracts either made public or leaked have four per cent in raises over the two years as well as a 0.5-per-cent lump sum payment.

Their benefits are also set to rise by four per cent each year of the deal.

CUPE's deal also included a commitment from the government to invest $115 million over the two years in special education and hiring office, clerical, technical and custodial workers.

Since CUPE was the first to negotiate a tentative extension, their deal included a clause that if another education union bargained higher wage increases, CUPE workers would be entitled to those percentages.

The tentative deal for the Elementary Teachers' Federation of Ontario includes an agreement from the government to cap full-day kindergarten classes at 30 students next year and 29 the year after. Currently, each school board must have an average full-day kindergarten class size of 26, but there is no cap.

ETFO's deal also included a commitment from the government to invest $89 million over the two years for school boards to hire special education teachers and for occasional teachers' professional development, early years special education support, and support for indigenous students, at-risk students and English-language learners.