STORY: It's the first day of first grade for these children in Ukraine.

Just months ago their school served as a bomb shelter.

And then a makeshift hospital.

Local residents hid here from Russian forces.

Now, it's welcoming back students for the school year – with the shelter still intact – as the war rages on.

Parents say all they can do is hope for the best.

“We don’t have a right to project our fears on our children. I saw the bomb shelter, it's in good condition. I hope the children won't have to go in there – but they have to learn and be among their peers."

Nearly 2,300 schools have been shelled or bombed since the Russian invasion began – including this school in Mykolaiv.

I want to go to school and see my classmates and teachers, says fifth grader, Arina Korchkova.

Air raid sirens go off as she speaks.

She and others are here picking up their books to study from home, the same as 95% of children in this region.

Viktoria Poliakova, deputy head of the school, says it's left her heartbroken.

"I remember that our school was very nice, it was very clean, it was very light. We had a lot of children, they were very happy at our school, so my heart is broken now.”

More than 350 children have died – with hundreds of others wounded – during what Russia calls a "special military operation."

That's according to U.N. data – but the real number could be much higher.