If you think your child or young person up to age 25 needs extra help at school/in further education, or to go to a special school/college, ask your local authority for an EHC needs assessment. Refer to The Children and Families Act 2014 Part 3 - legislation.gov.uk/ukpga/20....
If they have special educational needs they may be entitled to an Education, Health and Care Plan (EHCP). This will set out what their needs are and what they require to meet those needs. For example, a classroom assistant just for them. Or a school which has therapists on site. Or a school which specialises in people with autism.
If the local authority won’t agree to an assessment or doesn’t agree with what you think the child or young person’s needs are, you can appeal to an independent tribunal. You don’t have to have a lawyer and showing you mean business can sometimes make the local authority come to an agreement without a hearing.
Mencap has lots of advice about special educational needs on its website - mencap.org.uk/advice-and-su...