My school blocks blahaj.zonr due to "hosting pornography" but I've never seen that kind of content on this website ( I have nsfw hidden, but still) and the rules don't mention nsfw anywhere.
I live in Europe if that helps.
Unfortunately, LGBTQ-centric content is often labeled as "pornography" by the more reactionary forces of society, regardless of whether or not there's anything in it that's pornographic in nature.
I doubt your school did this deliberately, mind. But whoever built the filtering software did.