President Biden's hands-off approach to reopening schools amid the coronavirus pandemic is hurting America's children, Sen. Rand Paul, R-Ky., told "Justice with Judge Jeanine" Saturday.

"Being at home without any instruction ... for a lot of kids is a disaster," he said.

Paul said many students kept at home are now behind almost an entire grade year.  Studies show students who have returned to in-school learning have "already lost ground" academically and are performing poorly on tests, the senator added.

"Most parents just aren't capable of teaching," he said. "Some are extraordinary teachers, but a lot of parents aren't."

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As much as keeping schools closed will do "immeasurable damage" to kids, Paul claims the continued shutdown is scientifically unsupported, since virus transmission is not largely traced back to children or schools.

Experts, however, have pointed out that teachers and other school employees, from janitors to bus drivers, are at risk if schools aren't reopened safely.

Instead of teachers unions prioritizing getting students back in the classroom, Paul said they've been buddying up to the Biden administration.

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"When is the union going to actually care about teaching our kids?" he asked. "They have all these unreasonable demands even though ... the CDC, which is overly cautious, is saying that schools can open."

According to the Center for Responsive Politics, teachers unions upped their political spending to $43.7 million during the 2020 election, leaning heavily Democratic in their donations. The numbers reveal just 2% of teachers union donations in the 2020 cycle went to Republicans.

Biden has said his goal is to reopen most schools within his first 100 days in office but the administration's testing czar, Carole Johnson, has suggested that the timeline may be adjusted as needed.

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Fox News' Evie Fordham contributed to this report.