The con for me is that each individual school interprets the concept in their own way with no oversight. The one I was looking into for my kid many years ago was so strict with their rules it was scary. We did a trial day with my kid and we were instructed to not eat anything in the morning because breakfast is a very important part of the start of the day.
Breakfast prep with all the serving, singing and saying gratitudes took almost an hour, for a bunch of very small kids some of which had to get up at 5 am so that they could make it to school on time. It was excruciating to watch and they were clearly very hungry.
This ceremony approach continued through the rest of the day, with every little thing taking a lot of time and every kid was expected to religiously play along. It was enough for me to nope out and I didn't look into it anymore.