In Los Angeles, nation’s second-largest school district demands a negative COVID test — every...

As hundreds of thousands of kids return to class in the nation’s second-largest school district, they’re participating in what amounts to a massive public health experiment unfolding in real time: Every single student, teacher and administrator in the Los Angeles public schools must get tested for the coronavirus every single week — indefinitely.

Even the fully vaccinated are required to get tested. Those who test positive stay home for at least 10 days. And those who decline to get tested can’t come at all.

Along with multiple other protocols the Los Angeles Unified School District is implementing — including masking for all and mandatory vaccines for teachers and staff — it amounts to by far the most aggressive anti-coronavirus campaign undertaken or announced by a major school district in the United States. And it comes as classrooms nationwide struggle to return to in-person learning amid the delta variant surge, with some governors trying to block mask mandates even as outbreaks have shut down schools or delayed planned re-openings in Florida, Texas, Iowa and elsewhere.

In Los Angeles, by contrast, the vast majority of parents, teachers and students are embracing or at least tolerating the stringent measures the district has adopted, with fewer than 3 percent of the district’s 450,000 K-12 students opting for remote learning instead. And while it remains to be seen whether L.A.’s ambitious approach will prove successful in keeping the district’s approximately 1,000 schools open for the entirety of the school year, local leaders and public health experts say the district is raising the bar in a way that’s being watched closely and could influence educators nationwide.