They were once good students but Walid Maaruf, 11, and Ibrahim Ghaben, 12, had to quit school and earn a living when their fathers lost their jobs.
Israel and Palestinian militants in the Gaza Strip have fought three wars since 2008, including a devastating 50-day conflict in 2014 in the tiny Mediterranean territory.
Residents have lived under a punitive Israeli blockade imposed 10 years ago and their options are further limited by Egypt, which has largely kept its border with Gaza closed since 2013.
Nearly half the enclave's 1.9 million inhabitants live under the poverty line, with 80 percent surviving on humanitarian aid.
Unemployment has risen dramatically to reach around 45 percent -- one of the highest in the world -- forcing many children to become bread-winners.
On Sunday, the International Labour Organization marks World Day Against Child Labour, an initiative that has seen the number of child labourers drop to 168 million from 246 million in 2000.
But in Gaza the trend has been upward.
According to Palestinian estimates, child labour has doubled over the past five years, with 9,700 children aged between 10 and 17 now working in the enclave.
"My father is unemployed, he used to gather stones and scrap metal... but now I work," said Ibrahim who earns about 20 shekels ($5) a day -- toiling six to 12 hours -- to feed his family of nine.
The boy, who looks much older than his age, said he and his father used to transport their find on a donkey-drawn cart "but the donkey died".
All day long, often under a searing sun or howling wind, boys like Walid and Ibrahim scour flashpoint Beit Lahiya -- near the border fence with Israel in northern Gaza -- for scrap to sell to recycling firms.
Signup to our newsletter and follow us on Facebook and Twitter!
The area is attractive because of potential finds of lead from Israeli munitions, but also carries the risk of drawing gunfire from border guards.
"Most of the children who work do so in neighbourhoods along the border fence, and these are the poorest areas," said psychologist Aida Kassab from the Gaza Community Mental Health Programme.
Labour law flouted
"Sometimes these children are only five and yet they are forced to do a job which is not appropriate for their age, their physical or psychological state," said Kassab.
Akram Saeed, 14, said he spent years gathering scrap but now he wants out and would like to "learn a useful skill" to improve the lot of his four siblings and parents.
Help came in the form of a Swiss children's relief agency, Terre des Hommes, which helps families send their children back to school or to attend vocational courses.
"The phenomenon of children who work reflects the economic and social situation of the Gaza Strip," said Khitam Abu Hamad, who represents the NGO in Gaza.
"There is no job market in Gaza," she said.
Palestinian law bans children under 15 from working but "it is rarely applied", said Iyad Abu Hujayr of the Palestinian Centre for Democracy and Conflict Resolution.
He said enforcement has been hampered by divisions between the Islamist movement Hamas, which rules Gaza, and the West Bank-based Palestinian Authority.
These divisions have also allowed abuse by some employers who often force children to work a 12-hour day for as little as 20 shekels, he said.
And the situation is far from improving, said Hyam al-Jarjawi, who is in charge of children's affairs at the Hamas-run ministry of social affairs.
With each war, "there is more poverty and the more the number of child labourers increases", she said.