That’s a good question! If I were picking a TV for a classroom, I’d go for something good enough without spending too much. A large smart TV in the $600 to $1,000 range should work well for that kind of space. If it holds up nicely, you can always upgrade later to something in the $1,200 to $1,800 range.
Brands like Samsung, LG or Hisense usually have reliable options with clear pictures and easy smart features. Since older kids will be using it often, I’d just make sure it has a sturdy stand or wall mount and enough HDMI ports for whatever they’ll plug in. Something simple and durable will go a long way until you’re ready for an upgrade.