PORTLAND — A thee-year contract ratified today by the city’s teachers’ union includes a salary freeze that will save the school district $800,000 in the coming year, district officials announced tonight.

Teachers agreed, by a vote of 92 percent, to go without cost of living or step increases in 2011-12, said Kathleen Casasa, union president.

Step increases at the current levels would resume in 2012-13. The teachers would get a 3 percent increase in salary base in 2013-14, which would be the first increase in four years.

Casasa said she hopes the teachers’ salary concessions will help save some of the dozens of positions targeted for cuts in the proposed $91.6 million school budget for the coming year.

The school board has yet to approve the contract but is expected to do so. The teachers’ contract is expected to influence ongoing contract talks with three other school employee bargaining groups.

The ratified teachers contract also would increase the number of days that Portland teachers spend on instruction, increasing the number of days that students attend school to 180 days, exceeding the state’s requirement of 175 days.