Welcome to WebmasterWorld Guest from 220.127.116.11
As an educator myself, at first I was theoretically supportive of TurnitinBot until it came by my site. It requested robots.txt and then proceeded to ignore disallowed list.
Upon further investigation at their site, I found cached copies of my heavy content webpages. The very same pages I don't want copied - LOL
Yes, they sell their service, but so far they haven't offered me my cut.
I emailed them demanding they remove my property from their DB but never received a reply. I now ban them by UA.
You don't have 18.104.22.168 listed?