Taken together, these strikes amount to an unprecedented wave of teacher activism. For several decades, teachers’ unions generally shied away from striking. While strikes occasionally cropped up due to frustrations over demanding requirements and stagnant pay, they typically did so as isolated blips, generating little attention beyond the affected locale. A similarly significant period of teacher strikes arguably hasn’t happened since 1968, when large-scale walkouts occurred in Florida, Pennsylvania, Oklahoma, and New York City, along with smaller-scale ones in cities such as Cincinnati and Albuquerque .

Even that wave pales in comparison with today’s. Inconsistencies in the Bureau of Labor Statistics’ data-collection methods make it tricky to compare the two periods in quantitative terms. What’s clear, though, is that the eight major 2018 strikes—including the four high-profile statewide walkouts—involved a total of more than 379,000 teachers and school staff. Taking into account the current L.A. strike—which is poised to end after Tuesday, pending teachers’ ratification of their union’s newly inked agreement with the district—brings the tally to at least 409,000. The four major teachers’ strikes of 1968, by contrast, involved some 107,000 educators total, according to a Bureau of Labor Statistics analysis .

If nothing else, education-policy scholars, legal analysts, and labor experts tell me this wave is unprecedented in the terms that matter most: the stakes, the sentiments, the long-term implications. The walkout in Los Angeles is distinct from its red-state predecessors of 2018 in many regards—its participants are effectively facing off against a Democratic-controlled school district and state, for example, and a plurality of them are Latino, including many whose activist roots run deep . Still, the impact of this strike, which has shut down the country’s second-largest school district for more than a week, amounts to much more than a disruption to classes for nearly 500,000 students. It could go as far as helping to solidify this sequence of strikes as a pivotal moment in a 21st-century labor movement that is characterized by its radicalism and sense of collective action, suggests Charlotte Garden, a professor at Seattle University School of Law who studies labor.

Read: The unique racial dynamics of the L.A. teachers’ strike