15 and 16 years old? Execute them. They cannot be redeemed
You do know that Israel does not have the death penalty? The one exception that happened was Adolph Eichmann on May 31, 1962.
Quoting from Wikipedia ...
In 1954 Israel abolished the penalty during peacetime with the exception of convictions of genocide, crimes against humanity, war crimes, and crimes against the Jewish people.
Only one person has been civilly executed in the history of the State of Israel – Adolf Eichmann, who was hanged in 1962 after he was convicted in 1961 of participation in Nazi war crimes relating to the Holocaust.
The only other execution to take place in Israel was that of Meir Tobianski, an Israeli soldier in the 1948 Arab–Israeli War who was falsely accused of treason and executed by firing squad after being court martialed and found guilty.
Others, including Nazi criminal John Demjanjuk, have been sentenced to death but won appeals to overturn the sentence.
But God, who is rich in mercy .....