After a few posts and comments mentioning that educators are welcome to use our sims, it seemed prudent to make a formal post here.
Inworld, search for Enercity Park under Places. We have a stage there that may be used for small meetings (20-25 people). On the iliveisl estate (iliveisl.com, slurls are on that site as well) there are many places that are open to the public and free to use. The park above allows you to rez objects for an hour to practice building and filming.
Inworld, you can also search for Subquark Hax and look at Picks in his profile for a landmark. Similarly, you may search for Ener Hax, the estate manager, and also find landmarks.
In a browser, you can also use a slurl. Even though the map does not show any land, it does work. Here is the link to Enercity Park.