Hi there!
Personally, I think any class pets are a good idea. What a beautiful way to introduce kids to biology and stuff. Especially herpetology!
As long as you read up on the care sheets here, and make sure your husbandry is all adequate (especially your
UVB light, basking temps, and substrate) a healthy beardie would be a great pet. You can even teach the kids about how lizards need to absorb sunlight through their skin, which is why you have a special sunlight-mimicking (UVB) bulb!
An alternative to crickets is dubia roaches. They aren't able to hop or climb, so they're a lot easier to maintain than crickets, and they also have no scent to them (unlike crickets). Another alternative is black soldier fly larvae, marketed as Phoenix worms or calciworms; similar to dubia roaches, but so calcium-rich that they don't really require calcium dusting. I know mealworms might be an attractive alternative, but please avoid them as their tough exoskeletons commonly cause impaction, which is painful and can be fatal for a beardie.
I should mention though, beardies are poopers. When healthy, they have nice big wet poops. If I were you, I'd keep the substrate as tile and the basking spot as a basking rock, so that cleanup is easy to wipe up. I only mention this because I'm thinking about how I'd juggle kid-teaching and dragon-caring!
If you're considering any lizard in general, leopard geckos usually pick one spot of their cage to poop, and their poops are smaller, making them an easily-cleaned pet. (Please look at care sheets specific for leopard geckos though if you plan to get one. They have much different husbandry requirements than beardies.)