In the wake of sex assault allegations against a special-education assistant who has worked at McKinley High School for seven years, the school said yesterday it would review its policies to ensure a similar incident doesn't happen again.

Peter Chun, McKinley principal, said he would look at instituting new rules to make sure students are safe, including possibly requiring that doors be left open if a student is alone with an adult.

Gregory Keau, 30, was charged Tuesday with first-degree sexual assault stemming from an incident last week in a special-education classroom with a 17-year-old student. Police said Keau was allegedly assaulting the student when another staff member walked into the classroom, saw what was going on and confronted Keau before notifying school officials, who called police. Keau fled, but turned himself in Sunday.

Chun said Keau is on leave pending resolution of the case.

After the incident, the student told police that Keau had also sexually assaulted her when she was 16.

Keau has worked as a special-education assistant at McKinley since 2001 — his first and only position with the state Department of Education, officials said. A background check was conducted on Keau when he was hired, and it found a 1999 misdemeanor for driving without a license. In 2003, Keau was convicted of third-degree assault, but the school was never notified.

DOE officials could not immediately say whether the offense would have cost Keau his job if they had learned of it, or if employees are required to alert the department if convicted of any crime.

Sandy Goya, DOE spokeswoman, said the department will conduct an investigation into Keau's history with McKinley, his background and the allegations of sex assault. She added that the incident is isolated, and that sex assaults against students are exceedingly rare.

Advocates for special-education students agreed, but said the incident points to a need for another look at how schools monitor the relationship between assistants and students. Often, these aides work one-on-one with special-education students throughout the school day.

Most have never had any problems, but advocates said there is the possibility for abuse.

Susan Rocko, of the Special Parent Information Network, a group that helps the parents of special-education students link up with resources, said schools can make sure students are protected with simple measures, such as requiring that there are always two adults or more present or mainstreaming students in classrooms, rather than isolating them with an aide.

"If kids are in the mainstream of school life, it's harder for things to happen to them," she said.

But mainstreaming isn't always possible.

And Chun said there are also practical considerations, such as sometimes a student needs to discuss a private matter with an adult behind closed doors. He added that not all special-education assistants work with students alone. Some work with groups or with different students at varying times of the day. He declined to say whether Keau worked only with the student who was assaulted.

There are about 25 special-education assistants at McKinley.

Meanwhile, Chun said the incident has concerned some parents and angered staff members.

Chun sent parents a letter on Monday explaining the incident. He said he has gotten a few calls from concerned parents. Most were happy that he had kept them informed, he said.

Chun added that staff members have expressed anger over the incident.

"They're upset. It's just a very bad situation," he said.