There is no scripture to supports doctrine of “age of accountability”.
The concept did not come out from no place.
Jesus said of little chilren, ". . . for of such is the kingdom of God. . . ." The Greek word translated "little children" is παιδια plural of παιδιον.
Now a ruler named Jairus had a "little daugher" of a said age of twelve. The Greek for little daughter being, θυγατριον. The Greek ending -ιον meaning little.
So the age of accountablility has been supposed to be to the age of twelve. This is a deduced interpertation from Scripture. Since at birth a child was counted as 1 the age twelve should be our age of eleven.
What is important here is "little children" refers to children too young to properly discern good and evil or more improtantly to chose to believe said gospel for salvation. So their names would not have been removed from the book of life. So the need for the new birth to keep one's name in the book. Mark 10:15, John 3:3-4.
1 John 5:4-5, Revelation 3:5, Revelation 21:7. Revelation 21:8, Revelation 20:15, Revelation 21:27.