Hallmarks of Differentiated Classrooms

Carol Ann Tomlinson's book The Differentiated Classroom will be the subject of numerous posts as I encounter applicable points of discussion. In the first chapter, she summarizes some of the hallmarks of differentiated classrooms. Below she talks about one of the byproducts of creating an atmosphere where every student is challenged and suppported appropriately.

They (teachers of differentiated classrooms) work diligently to ensure that struggling, advanced, and in-between students think and work harder than they
meant to; achieve more than they thought they could; and come to believe that learning involves effort, risk, and personal triumph. These teachers also work
to ensure that each student consistently experiences the reality that success is
likely to follow hard work.

Now, imagine the students in your class. How many of them are challenged by the work at just the right level of difficulty so as to achieve success through just the right amount of effort - not needing to exert so much effort that they get frustrated and not needing to exert so little effort that they get bored? And, how does one skillfully manage assessment, diagnosis, curriculum, instruction, and time to make such an environment possible?