They were some of the most contentious negotiations in the Anoka-Hennepin School District in a decade, with teachers on one side trying to thaw a four-year pay freeze and protect health care, and district officials trying to control labor costs that make up more than 80 percent of their annual spending.

But finally — after 10 months, 18 bargaining sessions, a "work-to-rule" action by teachers and the prospect of a strike — the teachers' union and the state's largest school district struck a tentative deal shortly before midnight Monday.

Teachers negotiated raises, a $1,000 one-time bonus and some assurances on health care costs for the two-year contract that runs July 2013-June 2015. They also staved off a district proposal to add another step to the teacher seniority schedule but made some compromises on health care.

Anoka-Hennepin was the last large district in the state to reach agreement on a contract.

Teachers are expected to vote on the deal the week of April 14. If they ratify it, it would go to the school board for a final vote, possibly on April 28.

"After years of freezes, this contract does help us turn a corner," said Julie Blaha, president of Anoka Hennepin Education Minnesota, the union representing 2,800 teachers. "We made progress. We were able to hold back the divisive issue of adding an extra step in the contract for younger teachers. We were able to get some assurances on health care."

The district also lauded the deal.

"We are very pleased to be able to announce an agreement that we believe fairly compensates our teachers within the financial resources available to the school district," said school board Chairman Tom Heidemann.

Blaha said that having board members at the negotiating table the last two sessions helped the two sides find common ground.

"When you have the people who are making the decisions right there to talk to directly, that improved communication and helped make progress," Blaha said.

Under the tentative deal:

• All teachers receive a $1,000 bonus.

• Senior teachers, who make up 60 percent of the faculty, would receive raises of 1.5 percent the first year and 2 percent the second year. That group hadn't seen raises in four years.

• Less-experienced teachers would receive no raise the first year and 1.5 percent the second. (Less-experienced teachers will still see wage increases as they move up steps on the seniority schedule.)

• Both teachers and the district made concessions on health care.

• The pay raises are retroactive to the start of the contract.

Teachers will receive the first-year retroactive raise in one lump sum this spring. They will get the $1,000 bonus this summer and will be eligible for an additional $2,000 under Q Comp, Minnesota's merit-pay system, Heidemann said.

"Our teachers deserve it. There has never been a question about it," he said.

Heidemann said he'd like to sit down with the district's negotiating team later this spring to discuss "how we could have gotten this done faster and better."

Anoka-Hennepin, with about 39,000 students, is the largest school district in Minnesota. Under the new contract, the salary range will be from $39,000 for new teachers to $83,000 for those with more than two decades of experience and advanced degrees. The average Anoka-Hennepin teacher salary in 2012-13 was $62,300, eighth-highest in the state.

Salaries and benefits account for 82 percent of the district's general fund expenditures this year. That's $352 million out of $430 million.