You are welcome to answer questions posted in the Ask a Teacher forum as long as your suggestions, help, and advice reflect a good understanding of the English language. If you are not a teacher, you will need to state that clearly at the top of your post. Please note, all posts are moderated by our in-house language experts, so make sure your suggestions, help, and advice house the kind of information an international language teacher would offer. If not, and your posts do not contribute to the topic in a positive way, they will be subject to deletion.
If they're having lunch in the room used by all the teachers, you use "the teachers' room".
The apostrophe goes after the letter "s" if the noun is plural.
(If the room belongs to just one teacher, you'd write "the teacher's room" -- but I've never heard of a teacher having a room all to him or herself, so you probably need the plural version.)
teacher's 
Linear Mode
