public boolean deleteAllTeachersResults() {
   ExecutionCourse executionCourse = null;
   try {
     executionCourse = FenixFramework.getDomainObject(getExecutionCourseOID().toString());
   } catch (ClassCastException cce) {
     throw new DomainException("error.executionCourse.dontExist", cce.getCause());
   } catch (MissingObjectException moe) {
     throw new DomainException("error.executionCourse.dontExist", moe.getCause());
   }
   setProfessorshipOID(null);
   setShiftType(null);
   setInquiryQuestionOID(null);
   return executionCourse.deleteAllTeachersResults();
 }