But Samuel ministered before the Lord, being a child.
You are never too young to serve the Lord. Your particular gift may not be fully developed yet but the point is that if you are willing to serve the Lord, He will use you. One of our problems is that we are too busy doing our own business to be bothered making ourselves available for the Lord to use. Whatever age you are, make it your prayer to the Lord that you are available for Him to use, how and when He wants to.