Hello,
My beardie started out as a classroom pet, so speaking from personal experience.
Pros: Bearded dragons are very appealing to students (mine was in a 7/8 science room). There is a LOT you can teach with them (growth rate, metabolic pathways, ecosystems, adaptations, etc). It is good to have reptile "ambassadors" since many people don't like or care about reptiles. They are very personable and seem to enjoy the attention and activity.
Cons: They need food every day (babies more than once a day)-this means coming in on the weekends or taking your beardie home (stressful). Temps in school are very random (sometimes really hot, sometimes really cold), so it's hard to get temps in the tank right. Sometimes temps in the school mean that you need overnight heat sources, which is a (small) fire risk.
In the end, I decided that my beardie was going to stay at home with me. It was too difficult to have as a classroom pet. I may decide to bring him back when he's bigger, or he may come some days to visit. I do think I will get a lower maintenance reptile for the classroom (perhaps a snake or something). Although I love my beardie, and he is a welcome addition to my home, I wish that one of the many people I asked about a bearded dragon class pet would have talked me out of it.