They try and get you in the last 5 minutes of class and typically teachers address the important things first so if you leave you know whats up

I believe that students shouldn't attend ASI for not completing an assignment.

They either choose not to do the assignment or didn't want to complete it.They will probably not try thier hardest in ASI. So whats the point in assigning the ASI if they arent going to try their hardest?