update table

I have this table structure.

Table 1: Students
StudentID
StudentName

Table 2: ClassList
ID
StudentID
ClassName

I have a checked-listbox with all student names appearing.

When a user enters a class name (i.e. workshop) all students the appear with the class list are checked. This works a treat.

What I want to do is update/delete rows when students are unchecked or checked.

I thought, I could delete the entire class list and add them all again but that seems unnecessary, is there a better way?