Top juniors can be very, very different in meaning. The level drops off a lot once you get outside the top 5. The top 3-5 kids in any age group are most of the time way better than the rest. Surprisingly even a kid ranked 9th can be far below the top few kids in their age group.
I can tell you first hand how the very top juniors train in our area of S. FL. The 2 kids winning most of the tournaments train from 8-11 am, then back home for online schooling, then more training from 4-7 pm. That is M-F. Saturday is 4 hours of rotating practice matches. Sunday is rest.
The 8-11 and 4-7 sessions are 2.5 hours of tennis each....solid tennis with only water breaks, .5 hour fitness and stretching each session. Thats 25 hours training, 4 hours practice matches, 5 hours fitness every week.
Every other weekend they play a tournament.
Its amazing the sheer volume of work these kids put in.