A teacher used his mobile phone to film 'the backsides and chests' of schoolgirls. Paul Daw was also caught filming up the skirts of girls and young women on a busy shopping street.
Daw, 48, was caught after a mother complained to a community support police officer that a man had been 'following her daughter around the shops and filming her'.
When questioned, Daw admitted the images on his phone 'could be construed as offensive' and 'they might be indecent to some'.
Wirral Magistrates Court heard that Daw had become an 'obsessive compulsive' who was 'physically sick every morning before going to work'.
The teacher, from Bebington, Wirral, filmed pupils at the University Academy Birkenhead, in Merseyside, where he worked as an English teacher for more than 20 years.
He pleaded guilty to five charges of outraging public decency, and one of making an indecent image of a child, between March and December last year.
Altogether, 41 video clips of teenage girls were discovered on his phone from the school and shopping centres in Liverpool, Birkenhead and Ellesmere Port, Cheshire.
He was released on bail ahead of his sentencing next month.