Centers

I noticed that my classroom teacher is very "up to date" with her students in Literacy. What I mean by that is In the classroom, there are Reading Centers. The centers are ability grouped. While I don't particularly agree with that, I see the importance and functionality of centers. Each center has a certain activity and the teacher makes sure that each student performs each task before the end of the week. Also, the teacher knows exactly where her students are lacking and where they are succeeding and plans the activities for the centers accordingly. If she has to, the teacher will modify each activity according the students in it. I know that this should be a given in any subject and classroom, but I feel that some teachers just go along with the curriculum and not with the needs of their students.