I’ve worked with school systems that have crazy blocking. My guess is that they are blocking anything that looks like a forum because people are not supposed to use forums at work.
If that’s the case, all you can do is have someone in that institution request that your site be un-blocked (this requires that you find someone who can figure out who and how to ask for such) and then hope that whoever they contact is reasonable enough to look at your site, decide that it’s legitimate and unblock the site.
Good luck with that.