I've recruited several teens and people under 25. I am looking for a specific knowledge base in them which very quickly becomes apparent in their CV or covering letter and if they don't have it I move on, even if they sound like Einstein. Let's say for argument's sake I run a riding school so I need staff that ride and are comfortable with horses. I always specify that in the advert but I still get inundated with applications from people who have never ridden a horse or groomed one, but they love animals and had loads of posters of horses on their wall as a child, so it would be their dream job.
And then there are the ones who openly admit they have no knowledge of horses and no interest in them, but tell me all about the cafe they worked in last summer holidays. Then they say they'd be prepared to learn about horses if I gave them a chance, which I should, because they'd be really good. Well gee, thanks. How can I refuse an offer like that? 
But in generic retail jobs where there is unlikely to be much to separate the applicants, all CVs from youngsters with little or no work history will look roughly the same. Their exam results will vary but all the covering letters (written largely by AI) will ALL mention the same things. I've realised they run the job description through AI and you get the resulting response with all the things you asked for in the advert.
If I mention wanting a 'can do' attitude or good time keeping or strong people skills I'll get 50 emails that all say 'I have a 'can do' attitude and strong people skills. My time keeping is good.' It gets very tedious.
They will all have a 'passion for' something or other related to this job, even if the job is packing plumbing parts or mopping the floor in a restaurant. They'll waffle on about their hobbies and somehow try to relate them to the world of work, because it's all they have to go on, bless them. It's very hard to say anything that stands out.
They'll talk about being confident, enthusiastic, diligent, team players etc, etc and I can absolutely guarantee you that most of them won't be any of those things. Most of them will be monosyllabic twits who, once in the role, will announce they have anxiety or ADHD as a reason for why they can't do anything properly and who can't leave their phones alone for 20 minutes. There is very little to take from the generic CV of a kid who hasn't yet had done much, to help you sort out which five to interview out of a list of 200.
There's only one way to put any of those claims to the test and that's to meet them. But you can't interview 200 kids or you'd never get any other work done.
Group interviews with team exercises and question and answer sessions, role play etc are a great way of seeing who rises to the challenge and performs under pressure in front of other people. Who can sit and listen and not fidget or get bored, who can manage to not look at their phone for the duration of the group session. The interviewer will be looking for subtle things in candidates which might not be immediately obvious. They might be wanting to hear how clear your speaking voice is, see how you cope with eye contact, that sort of thing. See who arrives early and who is late. Set you up in scenarios such as 'here, would you like to take this chair?' to see whether you say please and thank you or just mumble and grunt. See who comes with a list of prepared, well thought out questions to ask, if invited to do so.
You'd think that the most assertive people would get all the offers in that scenario, but not necessarily. It will depend on the role. Sometimes the recuiter might be looking to weed out the over-confident 'ooh ooh, pick me' types. They'll know specifically what qualities they are looking for. It won't just be a confidence contest.
The other thing they will probably do is give the candidates some sort of questionnaire thing to fill out with a paper and pen. This will look at their literacy levels, hand writing, spelling, comprehension etc without them being able to rely on AI, spellcheck or anything else.