Hardly fascism. It's called safety, and they give up none of their rights to be required to blow into a machine as a condition of entry. I bet they also had to buy a ticket as a condition of entry. There may also be a requirement for appropriate dress. Are these all "fascist" requirements, too?
Relax a bit ... it's a school dance, a PRIVATE school dance, and they have a lawful right to compel kids entering to blow into a breath machine of they want to. The students can choose not to go ... or, to drink when they leave (unlawfully, of course).