A high school in the Hunter region of New South Wales has come under attack after the mother of a teenage boy with autism was told it was a mistake that he was invited to the year 10 formal.

Tyran Fennell has autism spectrum disorder and has trouble communicating, but has been attending Cessnock High School since year seven.

His mother, Deanne Fennell, said in a life where there has not been much to look forward to the formal meant the world to Tyran.

But the celebrations were dashed after speaking with a teacher at the school.

"The teacher told his mother that he wasn't meant to receive the invitation, what did I think he was going to get out of attending the formal, she didn't believe he would get a lot out of it," Ms Fennell said.

"I said back to the teacher I thought he would get what every other 16-year-old would get out of attending a year 10 formal, which was dressing up, dancing on the night and enjoying the night with their friends.

"[I was] absolutely gutted, I couldn't believe that in 2015 a teacher would respond in that way to me and that's why I've had to take things further."

She wrote letters to the school and held meetings with the school's management before being told Tyran is allowed to attend next Thursday's event, where he will be chaperoned by his sister Rhiannon.

Mother discovers Tyran also not invited to camp

But throughout this process Ms Fennell has discovered that a year 10 camp had been held throughout the year, something she had no idea about.

She said in another meeting with the principal, vice-principal and teacher, she was told it was "just an oversight".

(L-R) Tyran's brother Cody, sister Rhiannon, mum Deanne, Tyran and brother Rory. ( Supplied )

"I just said, 'Well, I can't believe if you've only got eight students in your [supported learning] class and how could you think not to invite to the camp'?" she said.

"Everybody in that year would've known about the camp and would've had a choice if they wanted to go to the camp or not."

Ms Fennell also held meetings with the Department of Education and said those meetings did not leave her feeling any better.

"The lady now that I spoke to at the Department of Education has come back and said the year 10 camp he wasn't academically suited to go [on], that was the answer," she said.

"I said to her, 'I don't get what you mean by that because you would still put support in and give him a choice over whether he wants to attend or not'.

"I am questioning now how many things he has been excluded from that I haven't known about."

A Department of Education spokesman said in a statement to the ABC that "all year 10 students were invited to the camp and formal".

"The school has worked closely with the student's family and teachers to provide appropriate supervision and support at the formal," the statement read.

"The school is reviewing its communications for such events.

"Cessnock High is an inclusive school, providing a caring and supportive learning environment."