My priority is a highly academic school that also give a wide range of opportunities in sporty, Community service, character building, innovation, and technology .. etc. Most importantly, a very high disciplined, strict culture..
Most Uk boarding schools will tick the sport, community service, character building etc boxes. I think if you are looking for rigid discipline you might be better off with a military type school in the US. Most British schools try to develop self discipline. The over subscribed ones are unlikely to be keen on a student who lacks this.
As an overseas boarder your son will want a full boarding school in which a majority of students are at school on a Saturday night. That is very important. There are not many of them.
I suggest you look at Oundle, King’s Canterbury, Marlborough, Uppingham in the first instance. All co-ed and academically selective. King Edward’s Oxford also co-ed is perhaps less academic but still has a strong cohort of bright children. All will be over subscribed in Y9 but may have the occasional vacancy in Y10 if a child leaves.
Beware of agents in Dubai. They will direct you to schools with which they have a commercial link. These are often under subscribed schools with high percentages of overseas students where all the British students go home at the weekend. This may not be what you are looking for.
Single sex - as pp said, I think you can forget Eton, Harrow, etc as they are unlikely to have any Y10 vacancies, although you lose nothing by asking! You might try Sherborne boys.
Charterhouse - single sex to 16 and coed in 6th form- has a high proportion of boys who go home at weekends, but are academically selective and play a lot of football.
Think about proximity to airports for flights. 12 transfers a year.
As pp suggest, look at the Good Schools Guide -though it rarely says anything negative about anywhere. And you could try a UK agent.
It is harder to fit in if you join in Y10.