Teaching

FILE- In this Wednesday, Jan. 30, 2019 file photo, Margaret Flynn, front, a 7th-grade teacher in Denver Public Schools, leads other teachers in a march during a rally outside the state Capitol in Denver. Denver teachers are vowing to walk off the job Monday, Feb. 11, unless they can reach a last-minute pay agreement with school leaders. (AP Photo/David Zalubowski, File)

FILE - In this Oct. 9, 2018 file photo, an embryo receives a small dose of Cas9 protein and PCSK9 sgRNA in a sperm injection microscope in a laboratory in Shenzhen in southern China's Guangdong province, during work by scientist He Jiankui's team. On Thursday, Feb. 7, 2019, a Stanford University official said that the school has started a review of interactions that some faculty members had with He, who claims to have helped make gene-edited babies. (AP Photo/Mark Schiefelbein)

Los Angeles Mayor Eric Garcetti speaks during a news conference Tuesday, Jan. 29, 2019, in Los Angeles. Garcetti will not seek the Democratic presidential nomination in 2020, slightly winnowing a field that is still likely to be large and unwieldy for a party desperate to oust President Donald Trump.(AP Photo/Jae C. Hong)

FILE - In this Friday, Jan. 18, 2019 file photo, elementary school teachers Iris Marin, center, and Mireya Gutierrez, right, and Lorena Redford, clench fists at a rally in downtown Los Angeles. Los Angeles teachers who declared a victory after a six-day strike have added momentum to a wave of activism by educators. They've tapped a common theme and found success by framing their cause as a push to improve public education, not just get pay raises. (AP Photo/Damian Dovarganes, File)

Students are welcomed with high-fives and hugs by teachers and administration upon their return to Evelyn Thurman Gratts Elementary School in downtown Los Angeles, Wednesday, Jan. 23, 2019, after a weeks longs city wide teachers strike. Thousands of Los Angeles teachers returned to work Wednesday after voting to ratify a deal between their union and school officials, ending a six-day strike in the nation's second-largest district.(AP Photo/Richard Vogel)

FILE - In this Tuesday, Jan. 22, 2019 file photo Los Angeles Mayor Eric Garcetti, talks during a news conference at City Hall in downtown Los Angeles. While Washington remains hobbled by a shutdown and deep partisanship, Garcetti says the resolution of a teachers strike shows that government can bridge divides and bring improvements to schools. "It's a national model for what we can do," says Garcetti, who plans to soon decide if he will enter the 2020 White House contest. (AP Photo/Richard Vogel, File)

FILE - In this Thursday, Jan. 17, 2019, file photograph, a teacher wears a button on a union shirt in the Denver Classroom Teachers Association, the union's headquarters in south Denver. Teachers voted Tuesday, Jan. 22, 2019, to authorize a strike, which would be the first called in 25 years in the state's largest school district. (AP Photo/David Zalubowski, File)

Marianne O'Brien, second from right, and her fellow teachers pose in downtown Los Angeles after rallying at City Hall, Tuesday, Jan. 22, 2019. A tentative deal between Los Angeles school officials and the teachers union will allow educators to return to classrooms after a six-day strike in the nation's second-largest district. O'Brien said she was ready to support the contract but would consider voting "No" if schools don't get additional support staff like nurses and counselors. (AP Photo/Christopher Weber)

FILE - In this Jan. 13, 2019, file photo, student Leo Rittner Solomon, 6, front left, and parent Hilda Rodriguez Guzman, right, react as United Teachers Los Angeles president and teacher Alex Caputo-Pearl announces the nation's second-largest school district, Los Angeles Unified School District, was going on strike in Los Angeles. The union said Monday, Jan. 21, that teachers are due back at picket lines Tuesday morning even if an agreement is reached Monday, saying it takes time to mobilize a ratification vote of a deal. (AP Photo/Damian Dovarganes, File)