A teacher showed an unhealthy interest in a difficult pupil in a bid to "groom" him for sex, a court heard.
Philip Nigel Evans who claimed he was trying to help the 14-year-old, took the boy on outings, bought him gifts and made or attempted to make more than 600 phone and text messages to him over a period of under five months.
But Durham Crown Court heard that the boy's mother was not always informed of some of the outings.
The boy told his mother that on one of them the teacher asked to see his private parts, and while in his bedroom, on another occasion, indecently assaulted him, while he was getting changed.
Anne Richardson, prosecuting, said during the period of the offences the boy was "no angel" and often truanted.
"Mr Evans ingratiated himself with the boy's family. The mother was at her wits' end and he told her he would keep an eye out on him for her."
But it emerged that although the school did have a "mentoring" system to assist some pupils, it was not in place in the boy's case.
Miss Richardson said: "Nevertheless, Mr Evans took him on outings and said it was a reward for good behaviour at school.
"What the Crown say was happening was that the boy was undoubtedly difficult at school and vulnerable, and Mr Evans was grooming him to be more compliant to any sexual activity.
"The fact he contacted him, or tried to contact him more than 600 times is not a normal pupil/teacher relationship at all, say the Crown.
"We claim he was obsessed with the boy, who may have had problems at school, but here was a boy who this defendant groomed, befriended, and when he gained his trust began to take him out without his mother's consent or knowledge in the hope of sexual activity."
Mr Evans, 34, was arrested at his home in St Cuthbert's Avenue, Chester-le-Street, and denied all the claims.
He denies indecent assault, indecency with a child and two offences of abduction.
The trial continues tomorrow.
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