Preserving some of the childhood for Syria's 'lost generation' of children There are more than 300 schools in Lebanon, teaching children from Syria.

The children inside Syria and the children who've escaped are still suffering, yet aid groups say they continue to try desperately to give some of the children a bit of their lives back.

Nearly four years ago, ABC News anchor David Muir and "World News Tonight" arrived at the Syrian-Lebanon border, boarding the back of a pickup truck and heading to the fields, where children worked.

Even after seven hours of hard labor, some of those children then attended class in a tiny school run by UNICEF.

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At the time, UNICEF's Sarah Shouman said that although she and others were trying to save at least part of the students' childhood, there was a fear that the children had become the lost generation.

"This is the big fear with everyone, including with UNICEF -- the fear of the lost generation," Shouman told Muir. "It exceeds boundaries. It's not only in Lebanon. It's in Syria. It's in Jordan. It's in Iraq."

Now, four years later, many of those same children remain in refugee camps. UNICEF said there are more than 300 schools in Lebanon, teaching children from Syria.

According to UNICEF, as of March 8, there were 546,536 registered Syrian refugee children in Lebanon. The organization estimates that around 180,000 Syrian refugee children are currently out of school.

With UNICEF support, the 2017 to 2018 school year witnessed an increase in student enrollment rates of 14 percent among non-Lebanese children -- Syrian and Palestinian refugees.

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And, in 2017, UNICEF and partners completed the rehabilitation of 123 schools, benefiting more than 43,000 children a year.

Yet, just last weekend, photographs and footage were released of a suspected chemical attack in the city of Douma, Syria, that killed and injured civilians, including children.

Carolyn Miles, president and CEO of Save the Children, said the organization is "heartbroken and horrified" by what children are facing in parts of Syria.

"These children are now trapped in the eighth year of a war whose tactics are growing increasingly inhumane. After years of living under siege and dodging bullets and bombs, this past weekend children were once again killed and injured in indiscriminate attacks," she said.

Miles said Save the Children was working through local partners to help, delivering food and hygiene kits to families who remain in Eastern Ghouta, and providing those who have fled with household items, food and cash grants.

"We are also building upon our existing programs in the country, including running medical clinics, schools, livelihood projects and a maternity clinic," she said.

UNICEF said that $14 could provide exercise books and pencils for children, including 40 exercise books and 40 slates for children to practice writing and arithmetic and a box of 80 pencils; $18 could provide schoolbags to five children; and $200 could provide a school box for 40 children.