What is a child?

In the New York Times article on Hezbollah last week, this was mentioned:

Hezbollah officials often casually mention the link between the Scouts and the guerrilla force.“After age 16 the boys mostly go to resistance or military activities,” said Bilal Naim, who served as Hezbollah’s director for the Mahdi Scouts until last year.

I have seen similar, offhand claims mentioned in the context of Palestinian Arab terrorist groups - they will recruit and accept teenage boys (or girls) as full members.

According to the IDF:

• Since the beginning of violence in the Al-Aqsa Intifada in 2000, 29 suicide attacks have been carried out by youth under the age of 18.
• Since May 2001, 22 shootings attacks and attacks using explosive devices were carried out by youth under the age of 18.
• Since the beginning of 2001, more than 40 youths under the age of 18 were involved in attempted suicide bombings that were thwarted (of them, three during 2004).

This is of course not something that started in the year 2000. This Life magazine cover from 1970 shows that clearly:
Yet the statistics that are given to the Western media will, without exception, refer to any Palestinian Arab victim in the violence who is under 18 as being a "child."

If one subtracts the numbers of child victims who are "young adults" from the total number of Palestinian Arab child victims, the total goes way down. Clearly a disproportionate number of Palestinian Arab children killed are 16 or 17 - 34 of the 80 listed in the PCHR annual report this year, with an additional 9 who were 15. This is hardly a pattern of indiscriminate violence against children when the majority of the victims are over 15.

Which brings up the question: if Arab society recognizes teenagers as being full adults in war, why should human rights organizations consider them children?