There is nothing more important in a relay race than a smooth hand-off of the baton from one runner to the next. The transition that baton makes between the hands of two runners sprinting at top speed demands precision and concentration. One slip, and the race is over.
After many years of student ministry, I cannot say that I have ever been pleased with the "handoff" of lives between children's ministry and student ministry. I see the evidence in the bored and disinterested 5th Grade students still hanging out with 1st graders as well as in the drop-out rate of 6th Graders who have been thrown into student ministry. You see it in the 5th Graders who would rather sit with their parents and doodle on offering envelopes in "Big Church" and in the consolidation of 6th Grade small groups because of the steady attendance decline. There is a reason why these students feel disconnected and they have been voting with their feet.