If you/your DH is still on the fence I would suggest talking to the principal and get some examples of what she considers to be "breadth and depth". I'm also so jaded by the system that I'd be demanding it in writing in the IEP so I'd have something to go back to later if needed.
As noted above, my conversation about photosynthesis with our VP made me quickly realize exactly what they were talking about. Hopefully it will help you determine if it will work for your kid.
I would also take a hard look at if it is differentiated teaching vs differentiated output. *Allowing* your kid to write 4 paragraphs instead of 4 sentences was generally seen as great differentiation in our previous school. When DS (who has a writing LD) didn't take advantage of this amazing gift - he clearly wasn't interested in enrichment/differentiation and they felt they were off the hook. Needless to say, DS wasn't thrilled.
Another thing to ask about is frequency. 20 minutes working in a small group with a resource teacher a couple times a year is one of the other things that they were very proud of. My DD was less than impressed with all of the other days that had zero differentiation. I should add that it involved them learning a game that we play ALL the time at home and then teaching it to the class. DD enjoyed it but I don't know that it was all that enriching or how it possibly related to math other than counting dots on dominoes.
It is also important to note that principals/VP's/admins aren't the ones actually doing any of this magical differentiation. You need a pretty amazing teacher to be willing AND able to pull it off. It also widely differs year to year because of this. I'd want to have some confidence that they will be willing and able to maintain enough differentiation for not just a year or two before making the jump since it is a one way ticket.
