The organizations warned of the dangers children face as schools remain closed.

Humanitarian organizations have warned that children around the globe face “unprecedented risk” as school closures related to COVID-19 drag on, and they’ve issued guidelines to assist in balancing educational needs with public health and safety.

UNESCO, UNICEF, the World Food Programme and World Bank on Thursday released joint guidance intended for the dozens of nations grappling with providing educational opportunities for nearly 1.3 billion students.

The organizations, while noting that there isn’t yet evidence to measure the effects of school closures on slowing the spread of the virus, said in a joint statement “the adverse effects of school closures on children’s safety, wellbeing and learning are well documented.”

“We know the longer children stay out of school, the less likely they are to ever return. Unless we prioritize the reopening of schools – when it is safe to do so – we will likely see a devastating reversal in education gains,” Henrietta Fore, UNICEF Executive Director, said in a statement.

The guidelines for reopening included policy reform, financing requirements, safe operations, compensating learning, wellness and protection, and reaching the most marginalized students. The plan is broken down into three phases: “prior to reopening,” “part of reopening” and “with schools reopened.”

Some of the specific measures suggested in the “prior to reopening” phase include reopening schools in areas with the lowest transmission rates, limiting openings to either a few days or to certain grades and developing clear protocols on physical distancing.

The “part of reopening” phase outlined that schools should increase access to hand-washing stations and cleaning supplies, as well as train staff on implementing physical distancing and hygienic protocols.

In the stage “with schools reopened,” the guidelines included actively monitoring health indicators and expanding the focus on wellbeing and protection.

The four organizations made a point to note that in many countries data on the virus’ full spread is not complete and that any reopenings must take that into consideration.

“Decision makers will need to make their best assessments in a context of incomplete information and uncertainty,” the joint statement added.

The organizations also urged schools to restore meal programs and health services to children in need.

“With many schools now closed because of COVID, 370 million children are missing out on these nutritious meals which are a lifeline for poor families. They are also being denied the health support they normally get through school,” David Beasley, the World Food Programme executive director, said in a statement.

UNESCO, UNICEF, the World Food Programme and World Bank all said that while the decision to reopen schools would not be straightforward, it should be a priority.

“Once there is a green light on the health front, a whole set of measures will need to be in place to ensure that no student is left behind,” UNESCO Director-General Audrey Azoulay said.

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ABC News’ Christine Theodorou contributed to this report.