Ontario's education minister will issue a directive to school boards Friday about $1.6 billion being put toward ensuring no teachers are laid off because of higher class sizes.

Boards will also learn their funding allocations for the next school year. The funding, known as Grants for Student Needs, will increase from last year — it was $24.5 billion for 2018-19 — though "not massively," senior government sources said.

The Progressive Conservative government has announced that high school class sizes will increase, from an average of 22 to 28, over four years. Average class sizes for Grades 4 to 8 will increase by one student per classroom — from a current 23 students to 24.

School boards have said that will mean thousands of teaching jobs are lost, and some boards have been issuing surplus notices to teachers, prompting worries that those people will be fired.

A large crowd gathered at Queen's Park to protest against the province's education changes on Saturday, April 6. (Tijana Martin/Canadian Press)

Education Minister Lisa Thompson has said no teacher will "involuntarily" lose their job and the government has set aside $1.6 billion in attrition protection to ensure there are no layoffs.

If a school board has 10 fewer retirements than expected, for example, it could afford to not lay off 10 teachers by drawing on the fund.

Thompson will issue a directive to boards Friday telling them that she expects them not to lay off any teachers because of her recently announced class size changes, the sources said.

Teachers' and education workers' contracts expire at the end of August, but the government is looking to start bargaining early, potentially as soon as Monday. Premier Doug Ford has warned against the possibility of strikes, saying teachers have "a great gig."

Thousands of teachers and supporters filled the front lawn of the legislature recently to protest the government's changes to education.

Boards and teachers have also expressed concerns about Thompson's announcement that starting in 2020-21, students will be required to take a minimum of four credits out of 30 through e-learning courses.