However, we cannot do the study or the thinking for you. This is part and parcel of the process of growing up. They went about on all fours, imitating children and babbling. But Jesus is not speaking about the physical attributes of childhood. Jesus and Paul are both right.
Childhood gives way to maturity, in physical, mental, and emotional development.
Moral reasoning also progresses. Spiritually we mature, yet our spirituality contains simple, childlike elements. Growing up does not necessarily mean growing away from the simple lessons learned in childhood. You are putting away immaturity for maturity, but part of that maturity is the maintenance of the uncomplicated, innocent aspects of childhood. Thus, when you are tempted to throw away childish things like worn-out toys that are no longer interesting, consider putting a few of childhood's characteristics on the shelf for later.