At what age should a child go to Boarding School?

I was visiting a friend of mine a few days back, she has an 8 year old son who will be in year four by the next academic session which means by age 10 the boy will be ready for secondary school. While  we were discussing along with her husband, he said he can't wait for their son to graduate from primary so the boy can be sent away to a boarding house, while the mother was stating her disapproval; I asked the the father if he thinks the boy is old and mature enough to handle the pressures of being in a boarding environment and the father replied by saying no child is too young for a boarding house as long as it's not a toddler then the child is old enough and that moreover children need to learn to be independent at an early age. So I gave this a deep thought and as much as it sounds like a good enough reason, I still have my reservations and I know you all might say that's my opinion but what is yours? Let's hear it.