It came after a 'wand' scanner was alerted to somebody possibly hiding a phone.
A group of six Year 8 pupils set off the alarm and were taken to a PE changing room, where they were searched.
In a letter of apology sent out to parents head teacher Zoe Johnson-Walker defended the action as a 'screening' rather than 'search'.
She said there was no physical contact and no male staff were involved. But some parents were not happy.
One father said: "My daughter felt embarrassed and violated for having to expose herself in front of other girls and teachers."
The reports suggested the scanner may have been set off by the metal wiring in a girl's bra and not a mobile phone.
Parentdish.co.uk contacted the school but had not received a response at the time of publication.