Tracking and teacher expectations work together to disadvantage minority students by placing them in lower level classes.
The tracking system is based on putting different students in different classes depending on their ability. The "good" students study together and the "bad" students study together. Such classes are meant to help both groups, but often end up hurting the "bad" students as they get a lower quality of education.
This hurts minority students because they run afoul of teacher expectations. Teachers might often perceive minority students to be less able than white students regardless of actual ability. When this happens, it works together with the tracking system and places the minority students in the lower level classes where they get an inferior education.