SINGAPORE - A 15-year-old student suffered psychological problems, an eating disorder and even considered suicide after she had sex with a teacher, a district court heard on Tuesday.

The Secondary 3 student experienced intense and prolonged psychological distress, feelings of guilt, shame, disgust and self-blame and had poor sleep during her sexual relationship with the teacher between September 2012 and January 2013.

The 33-year-old accused, a local merit scholar who is now unemployed, admitted to five of 10 charges - one of committing an obscene act with a young person by French kissing her mouth and caressing her breasts and four of having sex with her.

Community Court judge Shaiffudin Saruwan will sentence him on June 30 after hearing prosecution's arguments for a stiff sentence of six years.

Deputy Public Prosecutor Kavita Uthrapathy said the accused was the victim's form teacher in 2011. Towards the end of the year, they communicated with each other via WhatsApp text messages and over Facebook.

After an overseas trip led by the accused in June 2012, shortly after his engagement, the victim sought help from the accused with her studies. She also started to confide in him about her family and her struggles with her studies.

Soon, their communications got increasingly personal and he would engage her in conversations of a sexual nature. He also asked her to send him nude pictures of herself via text message and she complied.

Sometime during the September school holidays in 2012, he took her to his parents' flat at Kensington Park and committed the obscene act in his bedroom after they had watched a video.

The following month, he picked her up at Upper Bukit Timah Road and drove to a secluded spot along Rifle Range Road where he had unprotected sex with her.

He took her to V Hotel Lavender, a budget hotel at Jellicoe Road, on Nov 14 and told her to wait in the car while he proceeded to get a room. In the room, he asked her to perform oral sex on him and she agreed.

He handed her a female contraceptive device he bought overseas before they became intimate. They also had sex at his flat on Dec 10 when his parents were not at home.

Ms Uthrapathy said police investigations showed the last occasion they had sex was in May 2013. Two weeks later, he got married.

She told the court that when the accused started to have sex with the victim, she became conscious about the way she looked and started to diet.

The stress of school and having to keep her relationship a secret took its toll on the victim. After the accused got married, she sank deeper into a depressive mood and had suicidal thoughts by September. His marriage affected her psychologically. She felt angry at herself and started to scratch herself until she bled.

In November, she was warded for suicide risk and medical complications . She was later diagnosed with major depressive disorder, post-traumatic stress disorder and anorexia nervosa. The victim's father lodged a police report in February this year after he found out that the accused had sex with his daughter.