Christians: is a child destined to heaven up until a certain age?

Apparently not. The general consensus among believers is, I believe, that you cannot get into heaven unless you have been baptised. That's the whole point of baptism, to remove the original sin and make it possible for you to enter heaven. No exceptions.But I think you'll find that you get all kind of answers here from the believers in god. It's a case of 'whatever floats your boat'.

Infants do not need to be baptized. When a person reaches a point when they know right from wrong and can grasp certain concepts and make the choice to follow the teachings of Jesus or not, then they are in danger of missing out on Heaven by the choices they make or don't make. Usually this is around the age of 15, but that is not a solid number some figure it out sooner.

I think that a child goes to Heaven automatically until he is old enough to understand the Gospel when he hears it. That may be grammar school age. God is just, but He is also fair. In answer to your subsequent question, if a person never hears of Jesus, he is judged by God on the goodness of his life lived, then told about Jesus and gets a choice with the obvious answer...Now isn't THAT fair???

all children have their angels. mathew 18.10. when they become of age to know the difference between good and evil, then they are responsable to believe in christ. groundwire.net

Oh goodness...if you thought children of different faiths and such went to hell, why on earth would you worship that God? Makes NO sense...

Too much innocence to go to hell.