New York City Mayor Bill de Blasio announced a plan Thursday that he said would Significantly reduce the closure of temporary public schools That has frustrated parents and teachers across town over the past few months.

From Monday, public schools will only have to close for 10 days if four or more cases of coronavirus infection are confirmed in separate classrooms within a seven-day period, and only if the city’s contact tracing program determines that the infection originated within the school. So far, schools had to be closed for 10 days when two unrelated cases were discovered, regardless of the source of infection.

The mayor said earlier this week that he would get rid of the so-called two-case rule, which led to the closure of more than 200 temporary schools during the last two weeks of March.

The new rule now applies to individual schools, rather than entire buildings. Because many of New York’s school buildings house multiple schools, two cases of the virus in one middle school could force an elementary school with no cases on another floor to switch to distance learning for days under the old rule.

Schools with suspected cases will no longer close for 24 hours while health investigators determine if the cases are related, a change that would eliminate frequent short-term closures that were sometimes announced a few hours before the start of the school day. One or more statuses present in individual classrooms will continue to demand a temporary closure of that semester, but not necessarily the entire school.

The city will increase testing in schools where at least two cases have been found.

Teachers who are fully vaccinated – along with older high school students who will be eligible for vaccinations this week – will not have to go into isolation even when classrooms are in quarantine. As of last Friday, more than 65,000 of the approximately 147,000 Ministry of Education employees have been vaccinated.

Parents in New York City have until the end of Friday to decide if they want to shift their children from distance learning to a personal classroom.