West Yorkshire Police said the CPS had found there was not sufficient evidence to charge the teen with racially-aggravated assault of the Syrian boy.
U.S.-backed forces have captured Islamic State fighters tied to a January suicide bombing in Syria that killed four Americans.
Shamima Begum's lawyer Tasnime Akunjee said they have "strong but as yet unconfirmed reports" that her son has died.
U.S.-backed fighters trucked out civilians from the last speck of the Islamic State group's dying "caliphate" in Syria on Friday, eager to press on with the battle to crush the jihadists. More than four years after ISIS overran large parts of Syria and neighboring Iraq and declared a "caliphate," it has lost all of it but a tiny patch in the village of Baghouz near the Iraqi border. (AFP)