My oldest, now 19, has had a Claris rim brake road bike for 4 years now. In the first 3 years she rode it over 5000mi, did 7 or 8 centuries thru those years, and trained for an Ironman with it. The drivetrain is perfectly fine, its dead simple to set up and maintain. The only downside is its heavier and uses some steel where higher levels use aluminum or composite. Basically, there is some spot rusting on bolts or a couple sections of the derailleurs. It doesnt impact reliability or performance at all.
We have a bike with Sora- its fine. Same things- dead easy to maintain and is heavier than more expensive groups.
We also have a road bike with older 105 9 speed and one with older Tiagra 9 speed- the Sora bike shifts just as fine and has lasted years without issue.
I would use any of the groups for a kid that isnt racing and not think twice. Whichever you buy, just get some quality cables and housing plus quality brake pads. Those things can be felt.