Many developers of games like 1v1.LOL or generic io games create "mirror" versions of their game hosted on Google Sites. Since sites.google.com is a standard educational tool, network firewalls rarely block it.
But there is a problem:
If you want the true "rip-off" experience (the kind you see on a YouTube ad at 2 AM), look for titles like Blocky Battle Royale or Pixel Gun Royale on unblocked sites. fortnite rip offs unblocked