From the Meir Amit Intelligence and Terrorism Center (ITIC), 17 Sept 2014:
An examination of about a third of the names of Palestinians killed in Operation Protective Edge revealed several instances of children and teenagers serving as military operatives in the terrorist organizations. The examination also revealed instances in which the ages of Palestinian casualties were falsified by Gaza's Hamas-controlled ministry of health. For example, boys aged 15 and 17 were integrated into the terrorist operative networks; the age of a nine year-old terrorist auxiliary was listed as 24; and a terrorist operative in his twenties was listed as 13 years of age.
Children and teenagers in Gaza's educational system undergo basic military training in the schools and summer camps. Using them as auxiliaries and sometimes as operatives... is not limited to isolated cases although at this stage it is difficult to estimate the extent of the phenomenon.
Using a Child as a Terrorist Auxiliary and Hiding His Age
The ITIC's ongoing examination of the names of Palestinians killed in Operation Protective Edge revealed the case of a 9 year-old child, who was assisting his uncle, a senor Hamas operative in the ...central Gaza Strip. The boy and his uncle were killed in an IDF attack. They were listed as casualties by the Palestinian ministry of health. The boy ...was nine years old (born in 2005). However, according to the list issued by Dr. Ashraf al-Qudra, spokesman for the Hamas-controlled Palestinian ministry of health in the Gaza Strip, was 24 years old ....listing his age as 24 was not an innocent technical error but rather a deliberate falsification whose objective was to conceal the fact that a child was exploited for terrorist activities....
Using the Death of a Terrorist to boost civilian casualty numbers
[On the other hand] ...The Palestinian ministry of health listed Ibrahim Jamal Kamal
Nasr, from Khan Yunis, who was killed on July 18, 2014, as a "13
year-old boy." In reality, he was in his twenties and a
terrorist operative in Fatah's Abu al-Rish Martyrs Brigades. ...it was not an innocent technical error but the deliberate insertion into the
list of a "13 year-old boy" with a name similar to that of the terrorist
operative who was killed....
See the full report for many instances of detailed evidence.