William Whillock, 56, was arrested in front of staff and students at The New School in West Heath, near Sevenoaks, Kent, after the head teacher was told of the affair and alerted police.
He had been in charge of child protection at the school, which caters for "damaged" pupils who have been "emotionally scarred by abuse, bereavement, bullying or other trauma" and cannot get along in maintream education, according to its website.
