Aidan Brannan’s autism and learning disabilities mean he isn’t aware touching someone’s hair or asking them for a hug is not always socially acceptable.

He craves relationships with others, but when his approaches spark a negative reaction it can result in him becoming frustrated and, on the odd occasion, he has lashed out.

Such behaviour was manageable at primary school, but as Aidan, now 18, began to grow his strength and size made his behaviour more of an issue and his special school did not feel they could cope.

His mother Debbie Forsyth, from Broxburn, in West Lothian, said: “We accept Aidan’s behaviour became more difficult as he got older and he began to lash out more.

“The school made a risk assessment that he couldn’t go out into the community and they moved him into a different class without telling me.

“He went from a class where he was going out swimming, kayaking and going for walks in country parks to being kept in a classroom with two much younger boys.”

Even though Aidan had two personal assistants to accompany him on trips funded from his support budget, the school kept him in the classroom and his behaviour and state of mind deteriorated until he was eventually excluded.

The school tried to exclude Aidan twice, but when they were unable to do so they simply told his mother they had no space for him and she would need to keep him at home.

She said: “No young child should be kept in that room. He didn’t like it and he wasn’t happy, but they kept him there until the excluded him.

“They then said they no longer had anywhere where he could go. They made it quite clear that he wasn’t excluded, but they wanted me to keep him at home. We were pushed to breaking point.”

Aidan has now left school and is continuing his development with lessons on how to live independently with a team of funded staff.

However, his case is a familiar one to autism charities across Scotland who argue schools are excluding pupils unlawfully - without going following the law.

More than a third of more than 1,400 parents who responded to a survey on the experiences of autistic pupils who have missed school said their children had been unlawfully excluded in the last two years. Almost a quarter said this happened multiple times a week.

Charities Children in Scotland, the National Autistic Society Scotland and Scottish Autism said the research showed it was happening regularly.

The survey also revealed that more than a quarter of parents said children had been placed on a part-time timetable and 85 per cent did not receive support to catch up on work they had missed.

The three charities are now calling on the Scottish Government to work with councils to put an end to the practice.

Amy Woodhouse, head of policy at Children in Scotland, said: “This is not an isolated problem as it is occurring across the country, to children of all ages, in both special and mainstream provision.

“Autistic children are not receiving the education they deserve and are entitled to.”

Carla Manini Rowden, education rights manager at the National Autistic Society Scotland, said: “Sending a child home without formally excluding them is against the law, yet it keeps happening to the families we support and it is having a devastating impact on the education and wellbeing of children.”

Charlene Tait, deputy chief executive officer at Scottish Autism, added: “When a child is excluded from school, it is not only detrimental to their education, but it also affects their social development as they are often left getting little, if any, quality time interacting with other children.

“There is also a huge socio-economic impact on the family, as too often parents tell us that they are stressed, unable to spend quality time with other children and, in many cases, have had to stop working.”

The Not Included, Not Engaged, Not Involved report sets out nine demands for action.

These include stopping the use of unlawful exclusions and inappropriate use of part-time timetables, improving the availability of specialist teachers, reviewing the availability of appropriate placements for autistic children, and enhancing programmes of initial teacher training and continual professional development to improve understanding of autism.

The charities are also encouraging the public to sign an open letter urging John Swinney, the Education Secretary, to implement these calls for action.

A Scottish Government spokesman said ministers wanted all pupils to get the support they needed to reach their full learning potential.

He added: “We welcome this important work to show the educational experiences of autistic children.

“We are working closely with councils to improve the consistency in support across the country, building capacity and providing more career development opportunities for staff.

“We also fund a range of services offering advice, support and representation to ensure parents, young people and children are fully involved in decisions that are made about additional support.”