A middle-aged maths tutor groped teenage girls from Southall and Greenford while being paid to help them with their exams, a court heard on Monday.
Stephen Allison, 59, of Rivermead Avenue in Twickenham, denies 15 charges - eight of indecent assault and seven of sexual assault between January 1999 and his arrest in August last year.
The seven youngsters, all Asian, were aged between 11 and 18, and included girls from Slough and Hayes. They cannot be named for legal reasons.
Prosecutor Jonathan Hall told the jury at Isleworth Crown Court: "These offences were all committed in the girls' homes where he was giving private maths lessons.
"He took advantage of his position as a maths tutor to grope these young girls.
"Putting all the conduct together it is quite clear that he gets off by touching his students.
"He frequently stayed a lot longer than the allotted times while never asking for extra payment.
"All of his victims were embarrassed and upset and one of them who suffered his attentions from the age of 14 to 16, was terrified of the defendant.
"They were all scared to speak out. Their parents had paid good money for the tuition and they didn't want to say anything."
The court heard he went too far with one of them by touching her breasts "more than once", and she and her family reported the matter to police.
Allison did not answer police questions but gave a statement saying much of the leg touching was "encouragement" and if he touched any of them, including the last one, sexually, it was "probably by mis-take".
"When you look at all the behaviour together, it does not look like a mis-take," said Mr Hall.
"Some of the offences were witnessed by family members. Also, the girls told their mothers and sisters that they were not comfortable with this man.
"It is beyond possibility that an experienced teacher should have been persistently touching these students to encourage them.
"These girls were uncomfortable in his presence and found it very hard and embarrassing to go to the police or tell anyone what was happening."
The trial, expected to last two weeks, continues.