TORONTO -- As one Ontario teachers' union reached a tentative contract agreement early Thursday, another was ramping up its work-to-rule plans for the start of classes Sept. 8.

Details of the deal between the Ontario Secondary School Teachers' Federation and the Public School Boards' Association are being kept secret for now, but will be given to local union leaders later this week. Teachers will get details on the agreement and the ratification process at membership meetings that will be held after Labour Day.

"It took 29 frustrating days at the bargaining table, the assistance of three different mediators and an entire calendar year to finally get the management team to move off of their radical management rights agenda and come to an agreement, an agreement that in reality we should have achieved months ago," said OSSTF president Paul Elliott.

The union was still trying to get a deal for school support staff, and has bargaining scheduled for Aug. 28 plus three dates in late September, added Elliott.

"As much as this has been a frustrating year for our teachers and occasional teacher members and leaders, our frustration over support staff bargaining is even deeper."

The OSSTF agreement came after its talks with school boards resumed this week following a three-month break, and just hours ahead of a move by the Elementary Teachers' Federation to announce Phase 2 of its work-to-rule campaign.

Elementary teachers will not participate in any field trips, fundraising activities, training sessions, professional development sessions or respond to any electronic communications from the principal or vice-principal outside the school day except where student safety is involved, said ETFO president Sam Hammond.

"We will not at this time ask our members to stop their voluntary extracurricular activities," he said.

ETFO isn't scheduled to resume negotiations until Sept. 1.

"I want to be very clear. If we cannot get a deal at that table and get it sooner rather than later, as I said Monday, (school boards) and Liberal government: you are in for the fight of your lives," warned Hammond.

The school boards, which negotiate on behalf of the province, must also reach agreements with unions representing Catholic and Francophone teachers.

Premier Kathleen Wynne said she was encouraged by the OSSTF tentative deal because it proves the negotiations work.

"What we said could happen at the table has happened," said Wynne. "Of course we have some other groups that we are now in conversation with, but this is a very significant and happy day in terms of getting our kids back to school."

Wynne admitted the negotiations are challenging because of the government's insistence that it will not fund any salary increases until it eliminates an $11.9-billion deficit, which is scheduled to happened by 2017-18.

"I've been optimistic all along because I know that teachers and support staff want to be in school," she said. "Each table is separate, but it's a very good thing that we've been able to come to one agreement."

The Ontario English Catholic Teachers' Association was scheduled to return to bargaining Thursday -- the same day its members were to begin job action at a high school in Moosonee, which starts classes earlier than most schools.

Talks are also scheduled this month with the union representing Francophone teachers.

None of the teachers' unions is threatening a full scale strike at this point.

New figures from Ontario's Ministry of Education show there are 130,000 teachers in the province, up from 115,000 a year ago.