Teach your students to ensure there’s a delay between requests so they aren’t hammering anyone’s server, and follow the rules in the robots.txt. I’ve scraped more than a billion pages without any issues.
Why should I be treated differently than search engine spiders?
If somebody doesn’t want their site scraped then they can let people know with robots.txt. Get off your high horse.
It might be illegal in some jurisdiction; IANAL but I think you can just get out of that jurisdiction and scrape away if that is the case. It might violate some ToS but ToS isn't law; the consequences of violating a ToS are usually on the order of getting your IP banned.
What you do with the stuff you scraped can be ethical or unethical.