DO-granting US medical schools have curricula similar to those of MD-granting schools. Generally, the first two years are classroom-based, while the third and fourth years consist of clinical rotations through the major specialties of medicine. Some schools of Osteopathic Medicine have been criticized by the osteopathic community for relying too heavily on clinical rotations with private practitioners, who may not be able to provide sufficient instruction to the rotating student. Other DO-granting and MD-granting schools place their students in hospital-based clinical rotations where the attending physicians are faculty of the school, and who have a clear duty to teach medical students while treating patients.