@SteamLouis-- Your concerns are very valid. Let me give some general advice to you, don't join programs offering online courses and certificates. As you said, those programs are great ways for these private for-profit schools but they hold little value in real life. An airline company isn't going to be impressed that you have a certificate from an online course. So don't bother with those at all.
Unfortunately, there isn't an authority that rates schools that offer air hostess training. So it's up to you to do your research. I recommend selecting a school that has a high percentage of graduates with jobs in airlines. That should give you a good idea of how good the program is and how recognized the school. The school should be able to provide this information to you before applying, just ask them about it.