Yeshiva on chol hamoed generally is impractical – kashering a school or building a large scale sukkah typically are efforts and expenses that make things challenging. There is also the matter of some poskim concluding that there are some isurei melacha on chol hamoed which would add further challenges to school. Having said that, as a kid I actually did go to school on chol hamoed sukkos for limudei kodesh (like sundays) but the school determined it was impractical and stopped. Either way, lag baomer does not fall into this category. I think yeshivas should spend more time thinking of more thoughtful ways to help kids appreciate the significance of the day rather than full dismissal or trivial festivities. But that disrupts status quo do it’s unlikely any time soon to change…
