California high schools will soon be barred frombeginning class before 8:30 a.m., under first-in-the-nation legislation signed into law Sunday night by Gov. Gavin Newsom.

The public schools in America's most populous state have until July 1, 2021, to implement the new standard that bill author, state Sen. Anthony Portantino, insisted will "put our children's health and welfare ahead of institutional bureaucracy resistant to change," according to NBC Los Angeles.

"Shifting to a later start time will improve academic performance and save lives because it helps our children be healthier," said Portantino, a Democrat who represents the sprawling San Fernando and San Gabriel Valley suburbs of Los Angeles County.

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The legislation also bans middle schools from beginning before 8 a.m. A similar bill had been passed by lawmakers last year but was vetoed by then-Gov. Jerry Brown.

Backers of later start times claim teenagers, and their still-developing brains,need every extra minute of sleep possible.

The Los Angeles Unified School District — California's largest and the nation's second biggest school system — did not take a position on the bill before Sunday's signing, a district spokeswoman said.

"Now that it has been signed by Gov. Gavin Newsom, we will closely evaluate the impacts to our schools in anticipation of the bill taking effect for the 2022-23 academic year," the LAUSD representative said on Monday, adding that most L.A. campuses now begin classes between 8 a.m. and 8:15 a.m.

If support for later start times gains momentum, it could someday have at least some impact on schools across the nation.

In America's largest public school system, the New York City Department of Education, "95 percent of schools" start at 8 a.m. and "the vast majority fall between" 8 a.m. and 8:20 a.m., a Board of Education spokeswoman said Monday.

Chicago Public Schools is the nation's third-largest system, where students also hit the books early. For example, 4,500-student Lane Tech High School rings class into session at 8 a.m. while the 3,400 students at Taft High School are at their desks bright and early at 7:45 a.m.

High schools in Miami-Dade County Public Schools, ring their first bell at 7:20 a.m., according to a district spokeswoman Monday. However, middle schoolers now get to sleep in, with the first bell not ringing until 9:10 a.m.

"Classes begin promptly" at 8 a.m. at Coronado High School, in Henderson, Nevada. Coronado is one of the biggest schools in the Las Vegas-based Clark County School District, America's fifth-largest school system.

Data compiled by the National Center for Education Statistics showed the average start time for public high schools in the United States was 7:59 a.m. and middle schools 8:04 a.m., according to the most recent survey taken in 2012.

Carol Kocivar, a past president of the California State PTA which backs later start times, called Newsom's signature on the bill an act of "historic support for our students."

She also tweeted Sunday that the PTA, "parents and medical professionals" believe a later start time is best "for the health and safety of our children."

The bill had been opposed by teachers and districts, which argued that start times should be solely at the discretion of local educators.

"We should not set the bell schedule from Sacramento," said Assemblyman Patrick O'Donnell, a Democrat from Long Beach and the chairman of the Assembly Education Committee. "Sacramento does not know best."