Im also a teen that commutes to school by escooter. Segway-Ninebot is a pretty high-quality brand in my opinion. For the purpose you gave the Ninebot E2 or E2 Plus II is a pretty cheap but still solid fit. I currently use the C2 Pro, its a kids scooter and Im very over the max reccomended rider age for it but I its cheap and gets the job done for me. But except for the few times I go somewhere extra, school’s only 1.8 miles for me, and for his longer range its probably better for him to get an E2, E2 Plus II, or maybe even an F-series if you want to get fancy (though I doubt he’ll need the power of an F-series).
This is what I bought for my 12 and 14-year olds to use. It's enough to get them going and not too crazy fast. Still need to wear gear. They weigh 105-125lbs, and it's enough for them to get up the steep hill next to our house. I'm 180lbs, and I can ride it on flats, moderate hills, but it won't climb the steep hill with me on it.
PinKooky7604
