I was told years back when I asked that question of a school secretary that the school division had a program that absolutely positively blocked all porno. I said, "No way!"

I went to the library, typed in    sex    and was immediately whisked off to a photo of two ladies rubbing their upper body protuberances on each other. I then called the office and asked her to come to the library and see. That was the last I heard of sites being blocked by anyone.