Heres a hard question?

I want to know a film that came out during the eighties, Im pretty sure it was an Australian production. It was about a group of guys who take a clroom full of schoolkids and a teacher hostage, the guys were all wearing masks, Im pretty sure they were animal masks, one had a duck mask, and another had a pig mask (i think)...the kids end up fighting back in the outback, setting traps etc...might be a rubbish film by todays standards but I loved it when I was a kid...anyone know?