PHOENIX (AP) — As schools reopen for another year, they are focused on improving student attendance.

But back-to-school is hitting just as COVID-19 cases are increasing, raising the question: When is a child too sick for school?

School absences surged during the pandemic and have yet to recover. Nearly 1 in 4 students remains chronically absent, defined as missing 10% or more of the academic year, according to data by The Associated Press.

One reason for continued high absences: After years of COVID-19 quarantines, parents are more cautious about sending children to school when they might be contagious with an illness.

When a child misses school, even for an excused absence like a sick day, it’s harder for them to stay on track academically. So schools and health experts are trying to change the culture around sick days.

Here’s what they want parents to know.

COVID guidelines have changed

During the pandemic, the Centers for Disease Control and Prevention urged people who tested positive for COVID-19 to isolate at home for a set number of days and to quarantine after exposure to the coronavirus.

Those standards, and the caution behind them, remained for years after schools reopened to in-person instruction. That meant children often missed large portions of school after contracting or being exposed to COVID-19 or other illnesses.

This spring, COVID-19 guidance officially changed. Now, the CDC suggests people treat COVID-19 like other respiratory illnesses, such as the flu and RSV.

Fever-free for 24 hours

If a child has a fever, they should stay home, no matter the illness.

A child can return to school when their fever has been gone for 24 hours without fever-reducing medication. Other symptoms should be improving.

What about other symptoms?

If a child doesn’t have a fever, it’s OK to send them to class with some signs of illness, including a runny nose, headache or cough, according to schools and the American Academy of Pediatrics. If those symptoms aren’t improving or are severe, such as a hacking cough, call your child’s doctor.

The guidance around vomiting and diarrhea varies across school districts. Generally, students should remain home until symptoms stop, according to American Academy of Pediatrics guidelines.

“Unless your student has a fever or threw up in the last 24 hours, you are coming to school. That’s what we want,” said Abigail Arii, director of student support services in Oakland, California.

When to wear a mask

Masks and social distancing are no longer mandated but are encouraged to prevent disease spread. Experts also recommend plenty of handwashing and opening a window or running an air purifier.