It's believed 30 or more students from Bega High were informed only weeks out from the upcoming end-of-year celebration that not abiding by the school's uniform policy had cost them a place.

Many parents of the 15 and 16-year-olds took to social media to express their anger and disappointment at the school's decision, with a number of them also contacting the Bega District News.

Among them was Mel Britton, of Cobargo, whose daughter hasn't been banned from the formal, although several of her closest friends have.

She was in close contact with other parents and said she was speaking on their behalf given some weren't as comfortable coming out as publicly although they were just as "stressed and upset", especially as the short notice meant many students and their families had already organised and paid for dresses, outfits and booked hair appointments.

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"They've been looking forward to this all year," Ms Britton said. "They are good kids. It shouldn't come down to what colour shirt they've been wearing.

"No student should be punished for not wearing uniform - and this to me is a punishment."

In a response from the Department of Education on behalf of Bega High, the school said parents and carers had been advised last term and again this term that "participation in extracurricular activities including school socials is dependent on adherence to the Bega High School uniform policy, regular school attendance, and good behaviour".

"I'm all for discipline, but at least these kids are going to school," Ms Britton said.

"It's really trivial when you look at the bigger picture."

The Department said schools, in consultation with their school community, determine their own policies regarding school uniforms, and that "all students and parents/carers are aware of the Bega High School uniform policy".

"There is no excuse for students to repeatedly present for school out of uniform."