It is unhealthy to impose religion on children. However, I do think it's important to expose children to religion and its effects on the individual and society. This along with their continuing education in social studies and critical thinking skills will prepare them to make a healthy personal decision once they reach adulthood. Then let them decide which religious path (if any) they will choose.
The problem IMO with children being "taught" religion when young is that usually its purpose is to indoctrinate the child with the religious beliefs of the parent/family/culture of origin. This makes it easy to manipulate the child into being the man/woman others have decided they should be.