Any way to block sites without parental controls?

I'm a teacher and my school district has blocked us from changing parental controls from the ipad settings but I still want to block certain youtube searches etc. on my students' ipads without setting up guided access on 25 ipads.

I want them to be able to use youtube for classwork, I just want to block certain topics. We're working on digital literacy and self-control, but I'm beyond my own skills at this point.

TLDR Does anyone know of a way to block sites on safari without using parental controls?

Thanks!