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The back-to-school shopping season is off to a slow start as uncertainty swirls around if and when children will go back into classrooms, according to America’s biggest retailers.

The school shopping period typically extends from June through August.

But in the midst of the pandemic, school districts nationwide are struggling with setting an exact date to bring students safely back to classrooms. Some are going straight to a remote learning option at the beginning of the school year.

Walmart and Target (TGT) said on earnings calls this week that families were delaying purchases as a result.

“There’s something close to 56 million students in the K-12 bracket that are waiting to go back to school. And as of this week, it looks like well over 60% will start school remotely,” Target CEO Brian Cornell, said in a call with analysts Wednesday.

Uncertainty over when schools will reopen their campuses for students means families are delaying their back-to-school purchases.

“We don’t know if those students will be welcomed back into a classroom in September or October. Many may wait actually until January. So we’ve made the decision to be flexible. And we’ll extend the season and extend our assortment because we know at some point in time those students will need backpacks and uniforms,” he said.

While laptops, tablets and home office furniture sold well for Walmart (WMT)in the quarter ended Juy 31, basic school supplies, backpacks, and clothing didn’t, Brett Biggs, Walmart’s chief financial officer, said in a call with analysts Tuesday.

“[Back-to-school] is just slower than it would normally be, but that’s understandable given what’s going on with students and how quickly they’ll get back into classrooms,” he said.

For retailers, the stakes are high. The July-August school supplies shopping months are typically the second most important sales period for retailers ahead of the year-end holiday shopping season.

The National Retail Federation said in its annual forecast in July that spending on school and college supplies is projected to reach $101.6 billion, topping last year’s $80.7 billion and crossing the $100 billion mark for the first time.

But others are less optimistic.

Neil Saunders, managing director with GlobalData Retail, expects back to school spending will be down 6.4% from 2019 with consumers spending $26.4 billion on overall supplies as many students turn to a remote learning set up. The estimate does not include spending on college.

–CNNBusiness’ Nathaniel Meyersohn contributed to this report