Ontario is cutting the amount of money school boards receive per student, though marginally increasing the overall funding, and slashing several education grants by hundreds of millions of dollars.

The Progressive Conservative government announced 2019-20 school board funding Friday, coming as some boards have been issuing surplus notices to teachers, prompting worries about layoffs due to increasing class sizes.

Overall funding to school boards will be $24.66 billion, up slightly from $24.53 billion this year. But boards will get an average of $12,246 per pupil, versus the $12,300 they got in this school year, due to higher enrolment.

While the amounts of some specific grants and funds will increase, others are being cut or eliminated entirely. A grant given to boards with higher numbers of at-risk students is being cut by $230 million, to $514 million.

The pupil foundation grant -- which is the largest single component of the school board funding and is used for salaries of teachers, early childhood educators, and other education workers -- is $633 million lower than last year.

Education Minister Lisa Thompson announced last month that high school class sizes will increase from an average of 22 to 28 over four years, and average class sizes for Grades 4 to 8 will increase by one student per classroom.

School boards have said that will mean thousands of teaching jobs will be lost, but the government has insisted that can be done through attrition.

To that end, the government has established a four-year, $1.6 billion fund to top up boards who don't get enough teachers retiring or otherwise voluntarily leaving to cover the difference in staff needed due to larger classes.

"With this support in place, it is expected that school boards will not lay off teachers associated with the proposed changes to class sizes and e-learning," the ministry said in a memo to boards Friday.

Along with larger class sizes, Thompson also announced last month that students will need to complete four e-learning courses. Some boards have expressed concerns that online courses might not be right for all students, and that in rural areas students may not have reliable internet.

NDP education critic Marit Stiles said the latest funding amounts to a cut because it fails to keep pace with inflation and lowers the per-student funding.

"These cuts will hurt students, education workers and families," she said in a statement. "Classrooms will be overcrowded, programs will be cut and students will have even fewer opportunities and resources."

Several funds that the former Liberal government negotiated as part of education contract extensions -- to the tune of $281 million -- are being eliminated as contracts expire on Aug. 31.

The local priorities fund put money toward educational assistants to support children in need, at-risk students and adult education.

The amounts for adult day school teachers will be funded elsewhere, but whether that funding as a whole continues depends on the upcoming contract negotiations, which could start as early as Monday, the government said.

Laura Walton with the Canadian Union of Public Employees, which represents 55,000 education workers, said that money funded 2,500 educational assistants, custodians and clerical staff.

"We know that will be an absolute attack on education workers throughout the province," she said.

Walton said CUPE will fight for the continuation of that funding, but she is not optimistic, given that the government is currently consulting with the public sector on how to constrain compensation costs.

The government is working to eliminate a $11.7 billion deficit.