(NewsNation) — With class back in session in some parts of the country and just around the corner in others, one former federal education official is calling out plans to arm teachers and “harden” schools.

Students are beginning this fall amid a fraught environment. An ongoing teacher shortage has left districts scrambling to find qualified educators, while a surge in sales of bulletproof backpacks speaks to the rising fear of mass shootings. The worry is so high in some places that a county in North Carolina has stocked its schools with AR-15 rifles.

Former U.S. Secretary of Education Arne Duncan said arming teachers is a “terrible idea.” Duncan served under former President Barack Obama.

“It’s beyond heartbreaking,” Duncan said Sunday on “NewsNation Prime.” “We value our guns more than we value our children.”

The debate around school security measures resurfaced earlier this year following a mass shooting in Uvalde, Texas, that left 19 students and two teachers dead at Robb Elementary School. In the wake of the shooting, Congress passed the most wide-ranging gun violence bill since the 1990s.

School districts are ramping up security with measures including enhanced door locks, upgraded fencing and more resources for officers. But, Duncan said, there’s only so much schools can do to “harden” their buildings.

“You can’t harden arrival time, you can’t harden dismissal, you can’t harden recess, you can’t harden sporting event,” Duncan said. “We just have to get serious as a nation about protecting our kids.”

Schools are also facing teacher and bus driver shortages, which Duncan attributed to low pay and a lack of support among state leaders. Current Secretary of Education Miguel Cardona said Sunday states should use COVID relief funds to address the shortfalls.

“Using those COVID dollars is a great way to help teachers,” Duncan said. “We should be paying teachers a lot more.”

Addressing the myriad problems schools face is going to take a united and concerted effort, Duncan said.

“This is nation-building work,” he said. “If we can help each other and support each other, we can rise from this. We all need each other.”