Complex sentence: By the colonial era the gurukul system was declining in India except in a few regions, such as Kerala, where the warrior Nair clan and their own military "gurukulas", called Kalaris, still maintained the tradition.
Split into simpler sentences: By the colonial era the "gurukul" system was declining in India excepting in a few regions. Some in Kerala where the warrior Nair clan and their own military "gurukulas" called Kalaris still maintained the tradition.