What makes us and our teaching effective?

While Richard Allington's "Effective Teachers, Effective Instruction," I decided I was going to respond about "managed choice" (p. 278) and the importance of self-reflection (p. 279, #1), but then I read the following line as I finished up the essay:
"We can continue to craft curricular plans that will ensure some students will have to struggle. Or we can craft curricular plans that reduce the struggle for almost all students." (p. 287)

This brought - unsurprisingly - the differentiated instruction conference to mind. This is what good teaching is about. As teachers of our students, we must recognize that they all come into our classrooms at different places, and that they have different prior knowledge and different abilities. We need to find out where they are and who they are in order to figure all this out. We can't teach toward the middle and hope everyone does okay or teach toward the top and say that our high expectations will win out. We need to have the same expectations for all (everyone can and will be able to know, understand, and do x, y, and z), but we need to scaffold them up from wherever they are. Give everyone an equitable fighting chance - they all deserve it.

However, I have to say that I disagree with Allington's wording here. Struggle in the classroom is not an innately bad thing - students can engage more with a topic and learn more about it if they have to struggle with the issues and their depths in order to gain an understanding. However, we must ensure that they have the tools, the abilities, the motivation, and the encouragement to make them capable of winning; we must ensure that they have the self-efficacy to know that they can win the struggle and also have the desire to do so. It's hard to find a balance - when is it too easy? when is it too hard? - when we are trying to differentiate for our different students, but I think that it is vitally necessary.