SPRINGFIELD, Mo. -- Prosecutors have charged a longtime teacher at Missouri state schools for the severely disabled with abusing a young autistic student, alleging she slapped the boy in the head several times.

Janet Carrie Williams, 65, was charged Monday in Greene County with third-degree assault and endangering the welfare of a child, which are misdemeanors, The Springfield News-Leader reported.

According to prosecutors, Williams, of Lebanon, told police she "accidentally" hit the boy, who is 8 and unable to speak, in the head five times at the Greene Valley State School, one of the Missouri Schools for the Severely Disabled operated by the state Department of Elementary and Secondary Education.

Williams taught in the state schools for the severely disabled for 15 years, but her employment ended Jan. 2, the state Education Department said. It also said in a statement that employees at the schools are trained annually in the "zero tolerance policy against abuse."

The boy's family filed a federal lawsuit last month against Williams, Greene Valley State School, the state Board of Education and the state Department of Elementary and Secondary Education. It accuses Williams of violating the boy's rights and says he suffered "bodily harm and emotional distress."

The boy's father received an anonymous letter last year accusing Williams of slapping the boy "with an open hand," court documents show. He took the letter to the Springfield Police Department, which began investigating.

The lawsuit contends that while the boy was being physically and mentally abused by Williams, administrators noticed a "pattern of unsettling behavior" by her but failed to take "effective and prompt remedial action" to protect the child.

Williams' attorney in the civil case didn't immediately respond to a phone message seeking comment

A message left for Williams' attorney in the lawsuit, Denise Garrison McElvein, was not immediately returned Wednesday. No lawyer is listed for Williams in the Greene County case, and no one answered a call to a number listed under Williams' name.

Information from: Springfield News-Leader, http://www.news-leader.com