Good afternoon,
Yes.
A student with a diagnosis of ASD does not m ed to be assessed!
But if he needs extra time and the diagnostic report says so, since yr 8 he should have been offered extra time when needed in class and for tests so that now when you need to apply for this arrangement in external exams, it is already established as his normal way of working.
You need to just evidence this and write a senco note.
Normal way of working is key.
Hope this helps,
Jackie