Here is a picture I found of these TV sets. The one on the left seemed less common than on the right.
Ours did have a splitter so some teachers did use them to show videos, and on very rare ocassions we would just watch TV on them (such as right before Christmas break when there were few people in class). They all had basic cable channels. Most teachers that showed a lot of educational videos though had projection TVs that they used instead. And in my senior year of high school one teacher got a new TV for doing PowerPoint presentations on. It was a huge CRT, I think a Vizio brand, we never had an LCD or Plasmas then.