``It does concern me,'' principal Megan Odgers said yesterday.
Mrs Odgers has highlighted the issue in the school newsletter this week and she urged the ``community to be aware what's going on'' and to call the police immediately if suspicious behaviour was noticed.
Some people who were drinking at school grounds at weekends were not intending to injure others, but broken glass could have ``very serious'' consequences if pupils later accidentally cut themselves.
School grounds manager Gus Schaumkel said groups of about four or five teenagers sometimes drank at the school grounds at weekends, and the broken glass left on Saturday night was the worst since the incidents began in the middle of last year.
He had been at the school on Sunday and yesterday morning cleaning up seven patches of broken glass from the netball court.
Police have visited the school and are investigating.
Mrs Odgers said the school did not mind people visiting the area at the weekend ``but respect it the way we respect it''.
