It'll be prevalent but probably just very mild or asymptomatic in the vast majority of cases in youngsters.Local school seemed to be very few kids had it but lots of staff did! Maybe not so prevalent amongst youngsters?
It was reported on this forum many months ago that almost all kids had antibodies already (note: I know antibodies are not the 'be all and end all' of immunity; they're just easy to test for!) and therefore you'd expect cases to be milder, due to increased population immunity.
Also, back in the period of mass testing and isolation, many parents told me their child had to isolate due to testing positive but was absolutely fine; this was often a reason why the child couldn't participate in some activity, much to the frustration of everyone. Nowadays you simply wouldn't know as they wouldn't be testing.
Early on the Government said around 1/3 of people were asymptomatic, and that was before mass vaccination programmes and before most people got exposed to the full virus. Furthermore that's an overall estimate but we know that younger people are far more likely to have milder/asymptomatic cases than older people.
We also know that similar viruses (such as OC43) are very prevalent amongst kids; the vast majority of kids are exposed to all the common coronaviruses by a young age and it's simply a part of being human. We're transitioning to a stage where Sars-CoV-2 is simply added to the pre-existing four.