Is it possible to block all sites that come from an entire extension (such as .edu) from Adwords? If so, can you use www.*.edu in the blocked sites list?
You can always try to add .edu as the banned domain name. Not sure if it'll work, but you could always test it out. In that case, I'd add ".edu" without the quotes, and not go with *.edu.
What do you mean, block all the sites that are on .edu from AdWords? Are you referring to the content network? Most schools do not allow commercial content to be hosted from their servers anyway. Is there any specific why you're trying to block your ads from showing on all .edu domains?