Child visa (16 and 17 yrs) Required to prove English level ?

Our grandson has just completed his GCSEs with an Independent school in the UK. We plan to apply asap to extend his student permission to begin A level stage of his education with a new sponsor school in September.

He is Indonesian.
We are applying from in the UK. We are aware we will need a CAS from his new sponsor.
He is currently 17 and will still be 17 when he applies and when his course starts.
The new school's licence is only for 'child' students.

Therefore we assume he will be in the Child Student (16 and 17 yrs) bracket.
Our question is :Is a Child Student (16 and 17 yrs) required to prove English level (ie through a SELT) as part of his application.
He did not achieve English as part of his recently taken 6 GCSEs. He does have B1 through Cambridge PET but it was not a SELT format.
We know a child student under 17 is not required, and an adult student is required. But is it different for the 16-17 yrs bracket ?
Thanks for any help you can be
Nurmiani

If he is applying under Appendix child student, then no.

If he is applying under Appendix Student, then perhaps, as they may also accept sponsor assessment or GCSE English.

See also caseworker Guidance.