How old?

Once again I've been reading from the Old and New Testaments. The passage from 1 Samuel is about the calling of Samuel as a boy. God chose to use a child to talk to an old man; God chose a young person to tell an old person and supposedly wiser man what God has got planned for his families future.
I think this is brilliant! God chose the foolish things of the world to shame the wise; God chose the weak things of the world to shame the strong. 1 Corinthians 1:27 
Working with children is like this. So often I'll ask them a question or pose them a thought from scripture and they will come back with something really amazing. 
God doesn't discriminate who he chooses to use. He won't decide not to work through someone just because they are young, or a new Christian etc....The only thing God asks of us is to trust and believe in him. Our children and young people have just as much to offer for God's kingdom, for God's glory. Let's encourage the young to serve God with their whole heart and not be afraid or think that they are not old enough. Samuel wasn't, Jeremiah wasn't, Timothy wasn't and lets face it the disciples weren't too young either.