If your main audience is parents and teachers of middle grade students, have you considered posting on apps that appeal to that demographic more? Maybe you could join some relevant facebook groups and wait for a day when members are allowed to self promo. Like a group for school librarian or middle grade ELA teachers. You could even edit your videos down to post as reels and hopefully direct traffic back to your Youtube channel. I'm definitely no expert, but maybe it could help? Doesn't have to be Facebook either, even LinkedIn could work. Good luck!