SPOKANE VALLEY, Wash. -

Matthew Deryan, a Spokane Valley substitute teacher accused of "losing it" on a classroom of sixth graders pleaded not guilty to assault and false imprisonment charges in Spokane Superior Court Tuesday morning.

Deryan was already having legal problems including a recent DUI and a previous felony conviction for falsifying documents but school officials didn't know Deryan had been arrested.

The incident at Trent Elementary in the East Valley School District was a very rare one, but also illustrates the need to do ongoing background checks on our educators.

In all, Deryan entered a half dozen not guilty pleas including assaulting one couple's sixth grade son and three others. The parents, who declined to be identified, said their son reportedly suffered a concussion during Deryan's alleged outburst that left three students in tears.

"He got a concussion and has nightmares saying 'Ouch, please don't, that hurts, let go.'  He doesn't want any male substitute teachers any more," the parents of the student said.

Before Deryan became a licensed teacher he was fingerprinted and had to pass both state and federal background checks.

But since that time, Deryan has been restrained by a judge from seeing his own children and racked up a DUI in Kootenai County. East Valley school officials didn't know about Deryan's more recent run-ins with the law.

"I would hope they would come up in the WSP or the FBI checks, the problem is is that those aren't done on a yearly basis and so how we as a system become alerted to that is a significant challenge," East Valley Superintendent Dr. John Glenewinkle said.

Since Deryan's alleged meltdown, Glenewinkle has filed a complaint against Deryan with the state office that licenses teachers. It was apparently the first complaint against Deryan and right now school districts have to rely on teachers to self-report their own indiscretions.

"They're not going to tell them, "Oh yeah, by the way, I committed a crime, or Yeah, by the way, I got a DUI.' They're not going to tell them that. It's up to our school district to make sure our children are safe in the school," the student's parents said.