NEW YORK - Random monthly COVID-19 testing started Friday in 50 city public schools.

Between 10 and 20 percent of students and staff at each school are taking part in the program, led by city officials and the teacher's union.

Parents or guardians of students under 18 must fill out an online consent form in order for students to receive tests. 

The random sample of students will be tested one day a month and receive their results within 28 hours.

The state has also mandated that the city’s 308 yellow zone schools must start weekly testing.

That is expected to begin by next Friday.