Yes, it's a good idea. I have known a couple of teachers who have dated their students, one of whom ended up marrying her. But that is rare. If you find yourself unbelieveably attracted to him, try observing him when he's not teaching. Say, just hanging around talking with other teachers. Or, check out the people he hangs with. A person's associations are a good indicating factor of what they are made of. Teachers are notorious for putting on the charm, especially when their pocket book is involved. The best teachers are the ones who are truly honest with their students, giving them sound advice on their dancing abilities. You might be able to have them as friends, whether you continue to dance with them or not, but as for romance, that's another matter. You may find that seeing them outside the studio, out and about in public, shows them in a different light.

Just a small update, I'm still married to my former dance teacher and we now compete together in 'rising star' American style.
Once again, I want to emphasize that I DO NOT recommend trying to start a relationship with your dance instructor. It happened to us because of mutual attraction and NOT planning it.
Just use your head and be cautious.

This thread reminds me of a scene in "Shall We Dance" (remake) where Paulina says that she prefers not to socialize with students.

But then again, there is Johnny in "Dirty Dancing"...