SALEM — Oregon teachers’ salaries would be tied to their “classroom performance” under an initiative that’s won a spot on the November ballot. It is sure to spark a tough fight between teachers unions and the measure’s sponsor, Bill Sizemore.

The secretary of state’s office said Tuesday the measure had enough valid petition signatures to qualify for the statewide ballot, despite complaints by a union-backed group that some of the signatures were forged. Election officials are investigating the complaint, though they said the measure nonetheless has qualified.

The teacher merit pay plan would tie teacher raises and job security rights to loosely defined “classroom performance,” instead of on experience or seniority levels.

“The current teacher pay system is 95 percent based on seniority,” Sizemore said Tuesday. “Teachers get paid just for being there longer, without regard to whether they are doing a good job or not.”

A coalition of teachers, parents and education backers who oppose Sizemore’s initiative said it would do nothing to improve student achievement or teacher quality. They said it would only lead to more standardized testing in classrooms and more “teaching to the test.”

“We will fight to defeat this measure, because we know it is not good for our kids,” said Treasure Mackley, spokeswoman for the group.

In 2000, Oregon voters rejected a teacher merit pay initiative that would have linked educator salaries directly to student test results.

Schools and districts in about 20 other states have incentive pay plans, though the plans vary from place to place.

Sizemore said he purposely left the wording of the measure open-ended, to deflect criticism about forcing educators to teach to the test. He said merit pay could be based on classroom testing but also include peer review, supervisor evaluations or demonstrated student improvement.

“There’s no definition of ’classroom performance’ because I wanted that to be open and flexible so we can design a merit pay system that works for Oregon,” Sizemore said.

Five of the initiatives on this November’s ballot are sponsored or co-sponsored by Sizemore, who for years has been Oregon’s most prolific purveyor of conservative-tilted initiatives.

Three other initiatives have qualified as well, along with four measures referred to the ballot by the Legislature. In all, Oregon voters will be confronted with a dozen ballot measures this fall.

Tuesday’s announcement that Sizemore’s teacher merit pay plan has qualified marks the latest turn in a long-running battle between Sizemore and the teachers unions.

A jury awarded two of Oregon’s largest ones $2.5 million in 2002 after they filed an anti-racketeering lawsuit against Sizemore, claiming he used forgery and fraud to qualify two anti-union ballot measures in 2000.