Hollyhock, a Spirit of Mischief by L.T. Meade

There is nothing in its way more difficult than to start a new school; and Mrs Macintyre, with all her vast experience -- for she had been mistress of more than one of the celebrated houses at Cheltenham College in the time of the great and noble Miss Beale, and had in fact, until her marriage, been a teacher -- knew well what special difficulties she had before her, more particularly in a mixed school. There was no reason, however, why such schools should not exist, and do well. But she knew they had a fight before them, and that conflict lay in her path. She did not, however, know that this conflict was to take place so soon.

Mrs Macintyre was a good deal surprised by what followed Hollyhock's stolen visit to Ardshiel. The children -- boys and girls alike -- were now hard at work at their daily tasks. The first day passed splendidly. The Precious Stones became extremely great friends with Roger Carden, Ivor Chetwode, and Henry Anstel. There were also some other boys whose parents were negotiating to send their sons to Mrs Macintyre, for the fame of her school and the beauty of its surroundings were much talked of, and the idea of a mixed school highly pleased some people, while it equally annoyed others.