Sometimes. 
Sometimes.
But not with this .....
2 Samuel 5:4 KJV
(4)  David was thirty years old when he began to reign, and he reigned forty years.
1 Chronicles 29:26-27 KJV
(26)  Thus David the son of Jesse reigned over all Israel.
(27)  And the time that he reigned over Israel was forty years; seven years reigned he in Hebron, and thirty and three years reigned he in Jerusalem.
There is no place in scripture that says David was 13 years old when he became king.
If you want to teach scripture, then teach what scripture actually says. and stop adding to it.