The suspect, aged between 16 and 19, exposed himself in front of three girls aged 10 or 11 in the Nottingham suburb of West Bridgford.
As the girls walked past, he grabbed one to make her look.
Nottinghamshire Police said the indecent exposure took place on 15 June in Devonshire Road at about 08:15 BST.
The man, who left along a footpath on a disused railway line - known as The Green Line - is described as white, of slim build and about 6ft tall.
Neighbourhood Insp Craig Berry said: "On this occasion it [grabbing the girl] appeared to be more an attempt to draw attention to himself rather than anything else.
"But I don't know what this person's potential is so we do need to locate him."
He added there had been another incident with an older schoolgirl further down the footpath on the same day, and a third incident close to Loughborough Road, West Bridgford, three days later.
On that occasion the man, who fitted the description, was carrying a skateboard.
An artist's impression of a teenager wanted in connection with a sexual offence involving three girls has been released by police.