MANCHESTER, N.H. (CBS) - Several cases involving students assaulting teachers in their Manchester, New Hampshire classrooms have recently been reported.

There have been nearly two dozen incidents since the school year began. It's happening at all grade levels, at times disrupting class, and it's also costing taxpayers money.

School leaders are trying to step up their response to the problem.

In September alone, there were 21 teacher assaults that resulted in workers compensation claims. Teachers reported being bit, grabbed and punched, and in one case, a student headbutted an employee.

WBZ-TV's New Hampshire Bureau Chief Lauren Leamancyzk reports.

School officials did not say where these assaults happened. But, the superintendent is completing an investigation that he hopes will shed some light on where and why this spike is occurring.

"When teachers have workers comp injuries that is the result from students headbutting them, throwing things at them, pushing, biting and kicking, there's a problem. It's got to stop," said Mayor Ted Gatsas, the school board chairman.

Mayor Gatsas noticed the spike in reports when he was looking through his workers comp data. What's most disturbing to him is that many of the assaults weren't reported to police.

"Because no teacher, no student should have to go to school feeling like they may have to deal with a violent situation," said Ben Dick, a teacher and president of the Manchester Education Association.

Some students said it's a problem, but the violence is limited.

"All the kids here are actually really cool. But, there's just some kids here that just don't care and it makes it seem worse for the rest of us," said Tyrell Sweezy, a student.

The school board has directed principals to begin calling police anytime a teacher is assaulted.

Workers comp claims in Manchester have totaled $55,000 in just one month.