The Minneapolis school board approved changes Tuesday night in teacher and principal contracts that Superintendent Bernadeia Johnson says the district needs to boost performance at the city's worst-performing schools.

Both contracts were approved unanimously, unlike two years ago when some board members voted against a deal they said didn't go far enough.

"We were far apart when we started and everybody tried to put away some of those differences and do what's good for the kids," board member Alberto Monserrate said.

But teachers had more reservations about their two-year proposal. It was supported by 66 percent of Minneapolis Federation of Teachers members who voted, but that's down from 83 percent support for the previous deal in 2012. A rump group of teacher union members campaigned against the deal, although it drew praise from the union's national affiliate for allowing the union to help shape Johnson's partnership schools.

The two contracts allow Johnson to move ahead with those schools, where different work rules such as potentially longer work years and other departures from district norms could be proposed by teachers to design the schools they think would work better. Those schools would be required to meet performance targets to keep their freedoms.

The proposal could be put to work as soon as the reopening of Cityview school this fall. District leaders said they expect other reopening buildings — as well as those now struggling — to try the new approach.

The proposal also contains a number of changes designed to let the district seek outside hires earlier to stay competitive in the hunt for good teachers. Those are targeted mostly at vacancies at low-performing schools, and in harder-to-fill teaching specialties such as special education.

One improvement for some teachers is a district commitment to try to put no more than 18 students in each class for kindergarten and the first three grades, down from 21. That's only at lower-performing schools. But all teachers will have access to a new district hot line to report classes that swell over district guidelines.

The deal gives most teachers raises of 2 percent this year and 2 percent next year, with the initial boost retroactive to the start of the contract last July. Many teachers would also get pay gains from increases in their education or years on the job. The district publicized the increased two-year cost at $11.6 million, but acknowledged to the Star Tribune that figure is not a full calculation of all costs.

The board also voted to give the Urban League Academy, its worst-performing contracted alternative school, a one-year extension, after narrowly defeating a two-year extension on a 5-4 vote.