I agree with all that from arafelsings. To that, I would add that when trying to address the "sequential building blocks required to go from A-Z", in young beginners, most teachers don't break things down anywhere near enough, and take all kinds of things for granted that they don't even know they're taking for granted.
If you really want to address this, I would advise looking into specialised approaches to early childhood music education like Kodaly, Orff etc. (I wonder whether you could maybe do this through your college program?) Most of these are not piano-based, but that's partly the point. Young kids need to have experience of exploring music via singing, general rhythm playing, musical games etc, before the more specific and formal skills generally taught in piano lessons can really make sense to them.
I think one of the biggest mistakes we often make in music education is to forget the crucial role of INFORMAL musical experience. One of those teenagers comes to you for piano lessons and you call them a "beginner" - but they're not a beginner, at all. They've had 13 or 15 or however many years of hearing music, singing along, sharing music with friends, doing class music activities at school, etc. etc. All of that stuff is there, informing what they do when they first place their hands on the piano.
By contrast, an 8 year old has a lot less of that (some, of course, but less).
For me, this only started to make sense when I started teaching Kodaly-based musicianship in primary schools, and then using that as the basis for early piano instruction. I ended up spending ages creating my own custom materials (there are some available commercially, but I wasn't really happy with any of the ones I'd seen) but it was worth it.
The good news is that once you take it on, it's an endlessly fascinating field.