Case Statement Not Working as Expected

I am attempting to write a bash script that takes input from the keyboard and displays text depending on what number was entered:

#!/bin/bash
read -p "Enter your age: " AGE
case $AGE in
        [1-12]*)
                echo "You are just a child." ;;
        [13-19]*)
                echo "You are just a teenager." ;;
        [20-29]*)
                echo "You are a young adult." ;;
        [30-39]*)
                echo "You are a moderate age adult." ;;
               *)
                echo "You are really old."
esac

When you enter numbers like 3 or 4, it doesn't fall in the first range. It falls withing the 30-39 and the default. Where am I messing up?