No worries about his A-level options, but he will need to resit English
Will he though? His talents obviously lie in Maths/Science and he's clearly managed to do well enough in the written sections of these subjects (ie not formula/calculation based). It will be obvious to any Sixth Form or whatever they call themselves these days that he's capable of Alevels and probably a degree in these subjects too.
I got similar grades, As in Maths, Physics, Chemistry, but scraped Cs in English Language, Literature and History, but did well at science A levels and got a first in chemistry, despite hating essay questions and realising afterwards that I'd written my organic chemistry final paper in my own personal shorthand, which was a combination of the chemical formula and words
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Sounds like effort, study technique and staying off his phone will be more beneficial than a better GCSE in English.