Add respond to checks for teacher model.
Added Standard and Class Group.
Added GroupSubject which denotes linking between Subjects which a class group should have.
Linked Class Group to Subjects. Was some complex modeling phew :) .
Modeled Subject Standard which represents Subject of a parcticular Standard.
Modeled Teacher Subject Standard which represents linking between teacher and Subject of a particular Standard.
Linked Teacher and Subject Standards through teacher subject standards.