DI chapters 8-10

In chapter 8 it seems that the author is implying that it is ok to give different students different assignments. For some reason this idea seems not "right". What I mean is that logically it makes sense that having different assignments available would be the easiest way to create differentiation, however everything I've ever seen or experienced in a classroom makes me think this idea is wrong. Regardless, I like the idea of breaking the "invisible rule" that says all assignments must be the same. who really cares how many different assignments there are as long as they are equally challenging to each student? I totally understand keeping students on their "mental tiptoes" however I can speak from experience and say that keeping students challenged MUST be coupled with enough time for the students to understand the concepts. My algebra teacher junior year of high school encouraged me to take a difficult math class because it would challenge me and she "knew I could do it". I almost failed math senior year because I could not keep up with the math class I was in. It was only after we had past a new concept that I understood it whoch made "getting" the next concept nearly impossible. Time is IMPORTANT!