The Ontario Secondary School Teachers' Federation says the agreement amends components of the working conditions imposed in January by Bill 115.
OSSTF President Ken Coran says the agreement respects the fiscal parameters defined by the Ontario government and "problematic" issues in the imposed contract that were identified by members.
Under the new agreement, teachers will get improved maternity leave and sick day benefits, as well as fewer unpaid days off.
The changes reduce unpaid days from three to one for teachers, while support staff won't have to take any and can't be laid off unless enrolment declines, the government cuts funding for a specific program, or "catastrophic events."
Premier Kathleen Wynne has said no additional money will be spent to improve the contract, but opposition members have said they believe there will be extra costs.
PC education critic Lisa MacLeod says the Liberals need to "come clean" with how students will be affected by the deal with the high school teachers.
"School boards across the province are having difficulty covering basic costs for things like music programs, libraries and computers," MacLeod said Thursday.
"The Liberals need to be upfront with parents on which programs will be cut to be pay for this money-moving scheme that rewards unions and punishes students."
Education Minister Liz Sandals said she was pleased that OSSTF members voted in favour of the agreement.
"Our government and OSSTF have come a long way toward rebuilding our relationship in a collaborative approach which reaffirms our commitment to delivering excellence in our secondary schools for Ontario's students," Sandals said.