In special education, it often seems more important to know every last detail about our students, especially if they can't effectively communicate their needs. However, in my experience, I have noticed that the information presented in their cumulative folders and by previous teachers is often skewed. If the child had some difficult behaviors, these are amplified by the reports. If the child had a particularly endearing personality, this characteristic is too exaggerated.
As a result of this inherent bias, I sometimes think it is best to begin with a clean slate and allow my own experience with my students in an educational setting to define my teaching practice with them. By giving each student this equal opportunity, I am able to run my classroom with best practice in mind and afford each student the opportunity to be him or herself.