No training is a waste of time as you should always be able to learn something, even if it is don't ever do "that" again. However you do need to validate the cost of the training to what is being taught or can be learned to determine if it is worth spending your money on. Some private schools are very expensive and will get you fixed up with some very expensive student loans. which you get to start paying for even if you do not have a job. Let there be no mistake when you complete most 1 and 2 year training programs you will know and be able to do very little but you should have good understanding of the work you could be doing.

As stated the instructor(s) makes the whole thing work and worth while, Ask if they have a list of former student names you could contact. Ask for names of shops that have hired former students. Do an internet search of the school name and see what reviews come up (not from their website)

You are not likely to learn much in the 200 hour program you could probably learn more watching you tube videos

I would choose a 1 year diploma program in HVAC from a community college over a private school program, just my opinion primarily due to cost. I know what my local community collge offers and when you have completed it you are a good solid 1st year apprentice. You will have been exposed to the math you'll need, electrical and mechanical requirements, print reading, job shadowing with a local contractor and gain some actual hands of skills (soldering/brazing, hook up gauges, etc.) The cost, it just depends on your location, in my area a lot less than $1x,xxx for 1 year. My guess this should be comparable to the 900 hour private school but what's the cost of the private school?

Wheather you believe me (or others here) when you have completed 1 year schools you will know enough to have a conversation with a senior tech and know the tools when he asks you to get one (and how to use some of them) It's my experience that when you have completed your 1 year program you will have installed a simple residential (heating & cooling) system 1 time.

I'd ask the union if they have a waiting / testing list you could get on even if they say they have no apprentice openings at this time
Good Luck