The only classes that count as graduate classes are those numbered 5000 or 7000 and that are taught by a member of a graduate faculty. Cross-listed classes count as graduate credits, but only if they fulfill both of the aforementioned conditions. No 3000 or 4000 level classes count. Students can take them, but in addition to the normal load.
The only exceptions to this rule are language classes (within or outside the department), taken in order to fulfill language requirements.