It sounds like you have some school values in place that I would like for my child (combining grades and promising differentiation). In my opinion, when you have a perfect world where you get to choose, you need to look at school values and IB values separately. IB values are a constant, school values are a variable, and both are important.
The trans-disciplinary learning really is great. In the US, state standards tell you what facts and skills you must learn, and at what ages. Our Common Core that everyone is talking about suggests transdisiplinary learning, but it doesn't provide a methodology. From what I see, that's what IB provides--a framework that help schools integrate these themes and learner profiles with the work.
So an IB school has to provide BOTH the facts and skills that the state requires (or your national curriculum) and the collaborative, project-based, process-oriented methodology that IB requires. What that means to me is that while you may be able to teach to the test some of the time, you can't limit yourself to that and still be an IB school. I like that.
I may have just said the same thing twice, but you get the point.
