Education and Purpose

For another class, I recently read an chapter regarding differentiated teaching. Differentiated teaching involves finding and developing new ways to teach material so that students can discover what methods work best for them. Differentiated teaching encourages students to explore new avenues and test out different strategies for learning, while emphasizing the responsibility of the student in terms of his/her own education.
The main conclusion that I draw from differentiated teaching is that instructors should teach material with a direct purpose. Each strategy the teacher uses and each activity the student completes, should have a sound purpose, as opposed to the busy work that many students are expected to do. An example the chapter provides is that many teachers require their students to take notes during class. While note-taking should be encouraged, teachers should go one step further to ensure that their students understand the usefulness of their notes. Teachers should teach their students how to actually use their notes to further their learning on their own. In doing so, teachers have created a purpose for note-taking.
I suppose in relation to the subject of realism vs. constructivism, before deciding which philosophy belongs in the classroom, we should first examine the amount of purpose each one brings to the classroom. So, my question is this: How important do feel 'purpose' is in the classroom? Do you think 'purpose' motivates or encourages students?