Teachers can manage their assessment classes within My Subjects > Manage My Classes. Here they can remove themselves from a Class so they do not view the Markbook, or they can add/remove students from a Class.
In the Manage My Classes area teachers can see which Classes have been assigned to them and also remove any Classes which have been assigned in error (by clicking on the X).
Note: if any Classes need to be added, this can be done in Admin> Classes > Add Teachers to Class by a member of staff with an Administrator role.
Students can be added or removed from Classes in the Manage My Classes area too. Select a Class from the Class column, and you can click on a student to remove them from the Class, or search for them in the box to add them to the Class.