When students are dropped from the school's student information system, School Loop receives that information in the next data import - usually later that day. The next time you access your gradebook, you will first see an alert page letting you know which students were dropped. Click the Continue on to your Gradebook button to dismiss the warning page and open your gradebook.
By default, students dropped from your classes are automatically hidden in your gradebook, but it's a simple click to view and hide dropped students each time you need to view or edit their grades. In the upper left corner of your gradebook, as pictured to the right, there's a button that toggles your view of dropped students. Click to show. Click again to hide. Dropped students appear in your gradebook with a line through their names.