The tentative deal in Niagara was announced on Nov. 19 and had been approved by Education Minister Laurel Broten ahead of the vote.
The York Region deal had been reached two days earlier and also had been approved by Broten.
It's unknown by what margin the deals were rejected.
By rejecting the offer, teachers are expected to continue with job actions which include no staff and department meetings, no parent-teacher conferences outside of school hours and not submitting student attendance records.
Meanwhile, teachers with the Upper Grand district school board — which covers regions of Dufferin County, Wellington County and Guelph — ratified their agreement.
Four unions are taking the government to court, arguing Bill 115, which passed with support from the Progressive Conservatives, is unconstitutional.
The legislation gave the government the power to stop strikes and lockouts, and impose its own agreement if it doesn't like what the unions and school boards negotiate together.
(CKTB, The Canadian Press)