President Donald Trump’s attack on his own health experts’ guidance for safely reopening schools cracked open for public display a power struggle within the administration that has been building for months.

Trump blasted the guidance issued by the Centers for Disease Control and Prevention on Wednesday as “very tough & expensive” and “asking schools to do very impractical things.”

But CDC Director Dr. Robert Redfield said on Thursday the guidance would stand, and his staff would provide some new documents to clarify the recommendations.

Wednesday’s flare-up punctuates a conflict escalating for months, with the nation’s top scientists publicly sidelined in the Trump administration’s initial coronavirus response. Earlier disagreements delayed the release of the reopening guidance for schools and businesses.Public health leaders who worked at the CDC under prior presidents said they had never seen anything like this week’s open discord. Those signals can impair the guidance and the White House coronavirus task force itself, the experts said.

“It undermines leadership for everyone involved,” said Dr. Jeffrey Koplan, vice president for global health at Emory University and a former CDC director, who bristled at the idea that expense should drive school decisions. “I don’t remember hearing that for the airports and bars.”

“It’s public health malpractice to say, ‘Open without worrying about anything,’” he said.

The CDC’s current recommendations, which urge America’s frequently overcrowded classrooms to put six feet of distance between every student desk, have seen increasing scrutiny as communities grapple with how to safely resume classes as early as next month.

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The nation’s pediatricians, for example, recently called out the CDC’s six-foot guidance. It said such stringent distancing could do more harm than good by forcing schools to reduce classroom capacity.

The start of a new school year comes as many states, especially in the Sunbelt region, confront a surge in coronavirus cases after reopening everything from restaurants to day camps. The Trump administration’s loose guidance gave states and localities wide leeway on how to end a nationwide shutdown during the early weeks of the pandemic.