Three years of conflict are testing the resilience of Syrian children.

More than 5.5 million Syrian youth have been deprived of schools, food, medical attention, or a safe community to grow up in, according to UNICEF, which released sobering statistics on Syria's youngest victims days before the third anniversary of the crisis on March 15.

"The children of Syria cannot afford another year of conflict," states the UNICEF report, "Under Siege: The Devastating Impact on Children of Three Years of Conflict in Syria."

This week, NBC News is featuring "Forgotten? Syria's Children of War." The live documentary will unfold on Tuesday and Wednesday, following the lives of Syrian children over 48 hours on NBCNews.com, TODAY and Nightly News.

As of January 2014, more than 10,000 children had lost their lives to Syria's violence, according to conservative estimates from the United Nations — the highest recorded child casualty rates of any recent conflict in the region. And for survivors, days are bleak.

Last month, UNICEF workers found a five-year-old girl named Bara'a alone in the streets of Homs, one of the cities where the conflict has been most intense. Bara'a's mother had been killed by a mortar shell, but workers were eventually able to reunite Bara'a with her father — a rare sigh of relief in a country where at least 8,000 children have fled to Syria's borders without their parents, the report said.

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

About 3 million kids in Syria or taking refuge in neighboring countries — about half of Syria's school-age population — are unable to go to school on a regular basis because their schools have been flattened into rubble, turned into shelters or military bases. One in every five of Syria's schools has been destroyed, damaged, or transformed.

While education was once a priority for Syria, with primary school enrollment nearly universal for a generation and literacy rates over 90 percent, just making it through each day has become the new focus for Syrian families.

“Many Syrian children are in pure 'survival mode,'" UNICEF protection specialist Jane MacPhail, who works with child refugees in Jordan, said in the report. “They have seen the most terrible things and forget normal social and emotional responses."

2013: A brutal year

The past year has been particularly challenging: Since January 2013, the number of children affected by the crisis has skyrocketed from 1.8 million to more than 5.5 million. The number of children displaced inside Syria has more than tripled, from 920,000 to nearly 3 million. And the number of child refugees has more than quadrupled, from 260,000 to more than 1.2 million.

One in 10 children — over 1.2 million — has fled Syria, becoming refugees abroad. And once they leave Syria, their lives aren't necessarily better: One in 10 refugee children is believed to be working, doing odd jobs on farms, cafes or car repair shops, or collecting money by begging on the streets.

In the Za'atari refugee camp in Jordan, displaced Syrian children know the horrors of war all too well.

“My children see weapons and can label them. They know the names of each weapon, because they’ve seen so many,” one mother, who wasn't named, told UNICEF in its report.

The UNICEF report called for the international community to pay more attention to these children's plight — a plea echoed by international NGO Save the Children, which released a report on the health crisis among Syria's children earlier this week as well as a power public service announcement in the U.K. The minute-and-a-half long video depicts what's happened in Syria to one child as if it were to happen in London, following a British girl's life as it falls apart, and concludes with: "Just because it isn't happening here doesn't mean it isn't happening."

What's needed most

A lack of food for young Syrians is among the problems UNICEF hopes will attract more international attention: A doctor in Damascus, who did not give his name, told UNICEF teams, “We used to see one child with life-threatening malnutrition less than once per month. Now there are ten cases or more every week.”

Medical attention is also severely lacking for the tens of thousands of children who have been injured. Many doctors have fled Syria, forcing Syrian families to get care at overcrowded refugee camps in foreign countries.

To best help Syrian children, UNICEF called for a two-pronged international response: give aid to Syria itself, and give aid to the host countries that have been taking in Syrian refugees. It also called for a zero-tolerance policy on rights violations.

"Mechanisms already in place to monitor violations of International Humanitarian Law must be reinforced and supported," it said.

To find out how to help children in Syria, see this list of organizations working in the region.