Check with your exam board, but you don't have to be on stage to study drama. The non-exam assessments can be done from the design perspective.
We are wjec, and there are 2 NEAs. They work in small groups, that have at least 2 actors, and up to 4 designers. Design can be set/prop creation, lighting, sound or costume (including hair/make up). Those doing design do have to give a small presentation afterwards, but they are assessed on the content of the presentation rather than the presentation itself.
Depends if he eoyld feel comfortable doing that. Also depends on his English skills. They study a short play, and answer questions as part of the exam. ( similar to English lit).
If the school haven't given you copies, or links to information, if you know the exam board you can find out a bit more about subjects on the exam board website.
Ars there subjects he is enjoys more, is more interested in, or is better at.
We were told to look at what they enjoyed, what they were good at, and what they need for career choices.
Like others, when it comes to choosing options i think the school should adapt from the norm, if in the best interest of the child.