A Cornish music teacher was jailed on Thursday after taking advantage of a teenage pupil who had a crush on him.
The court heard how Neil Ellis, 28, who was also a special constable for Devon and Cornwall Police would frequently fondle the girl.
He pleaded guilty to sexually assaulting the girl when she was 14 and 15, and was told he had "exploited her immaturity and vulnerability".
Ellis, from Harrow Barrow, Callington, was jailed for 18 months.
Prosecutor Iain Leadbetter told the court the girl first met Ellis when she was at primary school and developed a crush on him.
When she was 14 they began to send each other text messages and this eventually led to indecency.
She told police that she felt she "did not have any choice" about what he was doing to her.
Mr Leadbetter said she was apparently "besotted" with Ellis and believed that they were a couple.
But he added: "She effectively felt that by the time she had reached the age of 16 he had lost interest in her."
Ellis pleaded guilty at Truro Crown Court on 18 February to four charges of indecent assault on the girl and four of inciting her to commit acts of gross indecency with him.
Judge Nicholas Vincent told him: "It is apparent that she developed a crush on you, and you exploited her immaturity and vulnerability for sexual purposes."
Ellis was sentenced to 18 months on each count to run concurrently, disqualified from working with children and told he would have to sign the sex offenders' register for 10 years.