It's statutory for all schools
The SEND Code of Practice provides statutory guidance on the SEND system for children and young people aged 0 to 25.
All schools must have regard to the code when taking decisions relating to pupils with SEN or disabilities.
This is explained on page 13 of the SEND Code of Practice and section 77 of the Children and Families Act 2014.
Involving parents and young people in decisions
Local authorities (LAs) must make sure children, their parents and young people are involved in discussions and decisions about their individual support and about local provision.
Schools, early years providers and colleges should also take steps to make sure that young people and parents are actively supported in:
This is set out in paragraphs 1.3 and 1.4 on page 20