DS is applying for comp sci apprenticeships so might be different but generally similar things have happened with most companies during the process if that's any use.
Generally they first send a CV and cover letter. So they need to make sure they have enough things going on to make a good CV. DS had done a lot of short courses, some volunteering, an EPQ, work experience, that sort of thing. Good grades and predicted grades definitely help. Cover letter obviously needs to talk about why they want to do this apprenticeship with this company.
Then there is often either a short phone interview just to check that you are not wildly unsuitable, or an online assessment. The online assessment often has personality tests where you rate how much you agree or disagree with statements and then there may be a few questions that you film yourself answering.
After that generally are the 'main' interviews sometimes online and sometimes face to face, might be a 70 minute interview, might be two interviews with different people, there might be a group task that you complete with other candidates. That's normally the end then, although JP Morgan for example, have another stage, they call an 'insight evening'.
It's quite an intense process, a lot of competition and definitely a bit of a numbers game. The more companies you apply to the more practice you get of the stages and the sort of questions you're likely to face - but you've got to balance that with the fact a lot of it happens around your mocks and you are likely to have to miss school for the 'big' interviews which sometimes go on all day - and they may have to travel quite a distance.
There are lots of positives though, it's made ds realise that if he goes to uni he needs to make sure he comes out the other end with much more than just a degree. He needs to be prepared to have a great CV with a lot of projects and extra curriculars to talk about at interview. It's taught him a lot about what to expect from personality tests, interviews, etc and he's seen that the more he does of them the more confident he has become because they often ask similar questions that he can prepare for ie why this company? Why an apprenticeship? Tell me about some group work you've done? Tell me about a time you've overcome adversity/solved a problem?
I'd say it's a generally a really good route to try for - ds had one company put him through all the stages and then email to say the recruitment process was 'on hold', but generally it's been a positive experience. I think it's good to keep other options open though (ie uni) just in case.