"As Ebbie and Sinsull said, an all girls school should be an all girls school"

And so it is Freda, no boys in class. Except those attending an indendently-run and funded club taking place out of school hours. The parents who are complaining would be completely within their rights if boys were introduced to classes/activities during the hours of normal school operation. Out of hours, it's none of their business, IMHO.