The "Know Your Air" Network includes 200 air quality sensors installed in schools throughout L.A.
It will allow students, families and school communities to check their local air quality in real-time, online.
Data from the network will also be used during emergencies and for research projects across the school district.
The U.N. health agency says nearly everybody in the world breathes air that doesn't meet its standards for air quality, calling for more action to reduce fossil-fuel use, which generates pollutants that cause respiratory and blood-flow problems and lead to millions of preventable deaths each year.
The World Health Organization, about six months after tightening its guidelines on air quality, on Monday issued an update to its database on air quality that draws on information from a growing number of cities, towns and villages across the globe - now over 6,000 municipalities.
WHO said 99% of the global population breathes air that exceeds its air-quality limits and is often rife with particles that can penetrate deep into the lungs, enter the veins and arteries and cause disease.
The Associated Press contributed to this report.