D.C. Public Schools Chancellor Michelle Rhee confirmed Friday that 302 school staff members, including 241 teachers, will not return to the classroom next year because of ineffective performance.

About 740 teachers and staff members were rated as “minimally effective” under the system’s new Impact evaluation tool, used for the first time in 2009-10. Those employees will not receive expected “step” increases — pay raises based on years on the job. In addition, if they don’t improve their rating by next year, they’ll be out of a job, too.

About 16 percent of the district’s 4,400 teachers, or about 700, were rated “highly effective” and will be eligible for performance-based bonuses under the district’s new teacher contract, passed earlier this month.

“When you have a system that produces 8 percent of its eighth graders on grade level, which is what we had when we came in in 2007, and 95 percent of the teachers were rated as effective at their job, you have to begin to bring those two things into alignment,” Rhee said.

Rhee batted down complaints from union officials who said the evaluation system was implemented too quickly, saying it had been developed and practiced over two years, with the input of nearly 1,000 teachers and staff.

The numbers — and the inevitable backlash — come amid a heated mayoral race. But Rhee said Mayor Adrian Fenty has remained supportive.

“The mayor said what he has always said — we don’t look at polling numbers when we make decisions about kids.”