Boko Haram training child soldiers

An organization associated with Boko Haram  named Al-Urwa al-Wuthaqa  have shown a picture which can be seen below where youngster are being trained, covered in black and holding weapons as they are being trained to be part of the sect Boko Haram

As boko haram have carried out mass abduction of children it may seems logical but how true  it is?