I go RPM classes which is the Les Mills International group cylcing class. Although the classes are all pre coreograhed (sp?) the instructors are allowed to mix and match tracks from the range of CDs produced (Les Mills bring out a new one every three months I think it is (the same thing for Body Pump which is their group weights class). If the system you are using is the same it could be that if they have only just introduced it the instructors only know one class and that things will get better as they learn new ones.

On the other hand if they system is that they have to all use the exact same tape for however long then yeah that could get boring