My kids will only use panniers if they are desperate for capacity beyond their backpacks, which usually only happens at the end of the year when it's time to take e-v-e-r-y-t-h-i-n-g home. Or if they're heading straight out for a sleepover.

When my son first got his most recent bike (a fixed gear), I wanted to have him keep a small saddle bag on it with a spare tube, CO2, etc. but he'd have no part of it. That sort of thing ruins the whole fixed gear aesthetic (silly me). And the reality is that he'd most likely ride 2 miles on a flat rather than change it even though he knows how to change one. So he doesn't carry that stuff. He's also not going to ride in the rain unless he gets caught in it so that eliminates the rain gear.

Basically, commuting by bike doesn't change the amount of stuff he'd have shoved into his backpack. They use iPads rather than laptops and that makes it easier.

Anyway, while he rode quite a bit from 6 through 8th grade that's not been case in high school. It's farther away (6 miles) and he's got stuff going on after school that keeps him there until 7:00 or 8:00 many evenings. I'm OK with him not riding in those circumstances. He's worn out and it's getting dark, plus there's homework that needs to be done. We've got car pools set up with his team mates and a bus gets him to school in the morning.

I am so glad my son grew into my old commuter w/ generator head and tail lights. No more nagging him to remember to turn on his lights as he dashes off into the dark fog.

My son rides his bike to high school a few times a week. It is only about 3.1 miles and half of that on a dedicated bike path which goes right by the school. The other half is on quiet neighbor streets. And here I often ride with him in the morning.
I just have to make sure he is using his lights and also wearing his helmet which he hates to do because of his hair he like to style a certain way. Teenagers.... Arghh... But I told him no riding without it.
Now I ordered some reflecting striping and I am going to upgrade mine and his bike to make it more visible in the dark. Just for safety reasons.
He is using a backpack but I already offered him to get some panniers which he as rejected so far.
My daughters school is too close and she walks with friends who don't have bikes. But she has a bike and she occasionally rides on the weekends and afternoons.