An alleged sexual relationship between a Bucks County teacher and a 17-year-old female student has resulted in the teacher's arrest and dismissal, and the resignation or suspension of three other teachers who allegedly knew about the relationship.

Robert C. Hawkins, a math teacher at Council Rock South High School, turned himself in to police yesterday morning. He was charged with endangering the welfare of a child and corruption of a minor after he allegedly had a five-month sexual relationship with the student, authorities said.

Hawkins, 43, who lives in the 1800 block of Society Place in Newtown, Bucks County, was released after posting bail, 10 percent of $500,000. His bail conditions say that he is not to have contact with the girl or any other minors, and that he must stay away from all Council Rock schools.

Hawkins could not be reached for comment. Marc Neff, his attorney, said that Hawkins was "an excellent teacher, well-respected by his peers and by his students." Neff added that "obviously, he's presumed innocent - these are charges, not convictions," adding that he would "reserve any further comment until I see what the nature of the evidence against him is."

The Council Rock School District, after conducting its own investigation, concluded that three other teachers knew about the relationship and did not report it to school officials or police, the district said in a news release yesterday. The police affidavit outlining the charges against Hawkins referred to e-mails between Hawkins and unnamed "associates."

One of the teachers has resigned, and two have been suspended with intent to dismiss, the district said. Neither district Superintendent Mark Klein nor Bucks County District Attorney Michelle Henry would name the three teachers.

Henry said police "are investigating whether other teachers were aware of the relationship and to what extent," but she would not comment further.

"This is offensive," she added. "Parents send their children to school for an education, not to be preyed upon by their teachers. This student is not just a minor, but one of his own students."

The district fired Hawkins in May. The girl's name was not released because of the nature of the crime.

According to a police affidavit, Hawkins and the girl began talking on the phone and text-messaging each other in November, with Hawkins initiating the conversations.

More than 6,000 messages were exchanged, police said, including messages from Hawkins saying he had checked to find out the age of consent for sexual relations. The two engaged in sex numerous times at Hawkins' home, from December to April, the affidavit said.

The affidavit also said that Hawkins had shown the girl sexually explicit pictures on his laptop of another female student at Council Rock South. Henry said authorities were investigating that, as well.