"board" by itself is not clear in American English. "blackboard", "chalkboard", or "whiteboard" would be much better.
Can "papan tulis" be used for plural blackboards if you're not trying to stress the fact it's plural, or do you have to say "papan-papan tulis"? I didn't accept "Our blackboards are still new."
How do you say 'whiteboard'?
Either /papan tulis/ (because of its function) or /papan putih/ because of the color.