The rape of a teacher by a teenage pupil has highlighted a continuing lack of communication between schools and other agencies, headteachers said this week.

The London borough of Westminster has launched an inquiry into why the school was not warned about the pupil, who had been identified as a threat five years previously.

The boy, who cannot be named, attacked the 28-year-old as she was marking books in her classroom after lessons. It was her second day in the post.

He threatened to kill her several times, bit her on the breast, headbutted her and pulled off her trousers and underwear. The struggle went on for about 12 minutes before he forced her to engage in oral sex.

It emerged this week that the boy was excluded from primary school at age 10 after attacks on pupils. His headteacher warned social services about his behaviour, but his trail of offences was masked because he attended several schools in various boroughs.

A report following his exclusion said he felt rejected because he did not know his father. He was apparently bullied while living in a hostel for the homeless with his mother.

Under the Children Act, schools, social services, police and other agencies should work in partnership and share information. But John Dunford, general secretary of the Secondary Heads Association, said the lessons of Soham had not been learnt.

“Again we have a violent attack by a known trouble-maker, but the school is unaware of his history,” he said. “The information flow between schools and other agencies is still one-way traffic. I can see no justification for not warning a head that there may be a potential problem on the premises.”

A Metropolitan police spokeswoman said: “We are working closely with our partners to see what, if any, lessons can be learnt, and looking to find out when this individual came to police notice.”

The teenager, who admitted the offence, had been in trouble with police three times during a six-month period prior to the rape.

He was believed to have been among a group of youths who threatened a girl with rape on a train in March last year.

The following month he was arrested after allegedly attacking a woman in Kennington Park, south London, but was not charged because of insufficient scientific evidence. While in custody for the rape, he was convicted of being in possession of a knife.

The teacher, who also cannot be identified, has been unable to return to work since the attack.

The Old Bailey heard this week that she was so badly cut and bruised after the attack that her colleagues did not recognise her.

The woman was alone in her classroom marking when the pupil came in.

Brendan Kelly, prosecuting, said: “She felt an arm around her neck, a strong arm. But she still, at that stage, thought that this was merely a student joking around. But the individual tightened his grip and pulled her out of her chair. He dragged her the length of the classroom.”

After a struggle he overpowered her and forced her into oral sex. The teacher retained the boy’s fluids in her mouth throughout the attack, and afterwards spat the contents into a paper cup.

The fluid was later used to identify her attacker. Closed-circuit television cameras also caught him on film as he escaped.

Westminster council said the school has since conducted an audit of its security and increased CCTV coverage.

A spokesman said: “We will be going to the area child-protection committee to find out what has happened.”

The head at the victim’s school said: “We regard this abhorrent crime as a completely unacceptable, but isolated, incident.”

The attacker was remanded in custody for reports and will be sentenced on June 17.