This is a lot less true than it was five years ago. Web browsing and basic word editing has not become harder to do in the past ten years, but hardware has made some major leaps. (thanks amd) So as long as it has an ssd and a semi modern (within five years) processor, it will do a great job of handling homework and 4k video. With windows replaced with linux, it’ll do all those things and feel snappy while it does it.

Avoid sub 100$ laptops, and keep a skeptical eye on anything between that and 400$, but it can absolutely be done.

I’m biased, but the dell inspiron laptops that businesses offload are perfect for this sort of task. They have connectivity out the wazoo (useful for that outdated projector in the seldom used classroom) and their batteries are easily replaced.