1: The teacher might be doing this out of ignorance 2: The teacher might be doing this out of insight 3: The teacher might be doing this because not everyone has high speed Internet.
If it is done out of ignorance, it is because the Internet is this big scary unknown that someone told them "anyone can edit" so they banned it. That is awful.
If out of insight, I've seen more and more students at the university-level think that an article is something they say on Buzzfeed. (Not kidding) By banning the Internet, it forces students to do more effort (sometimes literally because they have to physically travel to a library) to prove their point.
Lastly with high speed Internet, the upper-middle class were the first I knew to get high speed broadband back in high school. To this day, it isn't cheap where I live (is it for you? It is better now, but would still be a burden for many where I live) so banning the Internet puts an even constraint on students. (Before anyone mentions a computer lab, staying late at the computer lab is not the same as using wifi while you're bed or desk at home)
You should read a story called Harrison Bergeron.
Sorry for failing to be outraged. I don't helicopter my teenager... being challenged by schoolwork is on the list of things I hope for and a great use of technology would be J for mathematics class. Google and Wikipedia were part of the elementary school curriculum.
Good luck.
If that were my kid, I'd be asking for more context from the instructor/school on the situation. If the school's response isn't what I deemed acceptable, I'd demand either a change in the scope, or that my kid was placed in an environment that reflects how today's learning actually occurs.
Are there term questions along with essay questions? When I was in HS, the majority of homework had both.
Allowing everyone to just Google the answers has created a situation where people can't critically think for themselves.
There's a famous section in Plato's Phaedrus which gives an argument against writing on the grounds that it will both damage the memory and lead to unoriginal thought (since people will just repeat arguments that they've read in books, rather than coming up with original ones).
Learning to use a search engine effectively is a valuable skill in its own right, and no, "everyone" doesn't know how to do it. Watch some people thrash around with Google some time and I think you'll be surprised at just how bad they are at it.