Since he is going to study maths and physics at A level, then he should not drop triple science. Especially if applying to selective sixth form.
I would consider dropping the language so he can do both history and geography. There is no sixth form for uni requirement for a language unless you want to study it at university.
My niece took following GCSEs- Eng Lang, Eng Lit, RE, Triple Science, geography, Maths, Further Maths, Computer science and Design Technology. She dropped a language so she could do both computer science and design technology. The school will never suggest this because you need a language for the English baccalaureate or eBacc. The eBacc is not a qualification or necessary or of any advantage to the student, it is purely goes into how the colleges are rated by Ofsted. The more students leaving college with eBacc, the higher their rating. But it isn’t always in students best interest, so you can drop that language.
She wants to be a robotics engineer. She is taking the following A levels
physics, Maths, Further Maths and computer science.
(She already knows another language anyway, Chinese.)