Steven Greenhouse was the labor and workplace reporter for The New York Times for 19 years. He is author of the forthcoming book "Beaten Down, Worked Up: The Past, Present, and Future of American Labor."

The overall number of strikes by American labor unions has declined sharply decade by decade, an unmistakable measure of organized labor’s diminished clout. But last week’s strike by more than 30,000 Los Angeles teachers belongs to an extraordinary surge in recent union militancy — a surge that includes statewide teachers’ strikes last year in West Virginia, Oklahoma and Arizona, as well as ones by 7,700 hotel workers in eight cities last fall.

The L.A. walkout was particularly unusual in that the teachers won more for the kids than for themselves — the school district agreed to hire 300 more nurses so that every elementary school would have a nurse five days a week, and 84 more librarians so that every middle school and high school would have one.

Even though much of labor remains in a defensive crouch, the unions and workers joining the recent strike wave took to the streets with picket signs because they were fed up. In the teachers’ Facebook groups in West Virginia, Oklahoma and Arizona that helped ignite the strikes in those states, hundreds of teachers voiced such a burning sense of unfairness that they felt they couldn’t take it anymore. The teachers and their students were lagging badly behind, their pay stagnating, their school budgets squeezed when so many parts of the economy were booming, when corporate profits, the stock market, the incomes of the richest Americans were at or near record levels, and Congress and many states where handing out big tax cuts to business and the rich. Similarly, the Marriott hotel workers who went on strike in Boston, San Francisco, San Diego and five other cities were furious that their wages were not keeping up with inflation, and especially not with soaring rents, all when Marriott was making record profits.

Recognizing that unions are often isolated and under attack, those that struck went to unusual lengths to win strong community support, framing their demands with an eye to maximizing public backing. The L.A. teachers trumpeted their embrace of a new, community-minded strategy called bargaining for the common good — negotiating to help the students and the schools, and not just to improve the workers’ wages, benefits and working conditions. When teachers struck in Oklahoma City last April, many carried signs saying, “I am standing up for your child.” During the Marriott strike, meanwhile, room attendants and bellhops carried signs that also had a powerful message aimed as much at a broader American audience as at corporate management: “One Job Should Be Enough.” Marriott workers told me they often had to work two, even three jobs, to support their families, and that passersby who chatted with them voiced strong support for the idea that workers shouldn’t have to work more than one full-time job to survive. It was the private-sector version of bargaining for the common good.

There has never before been such an explosion of teacher strikes: More than 400,000 teachers and school staff walked out over the past year. Public-sector workers do not walk out lightly — many haven’t forgotten that President Ronald Reagan fired more than 11,000 air traffic controllers when they engaged in an illegal strike in 1981. Workers are mindful that Reagan and many corporations have used permanent replacement workers to take away strikers’ jobs. Those moves have led to a greater timidity and defensiveness within labor. Nearly 15 million American workers belong to unions, with the percentage of workers in unions sinking to 10.5 percent from 20.1 percent in 1983 and 35 percent in the 1950s.

In the recent strikes, that defensiveness was overcome by a fierce sense of unfairness. Teachers in Oklahoma, with pay averaging $45,276, were angry that they hadn’t received an across-the-board raise in a decade, while in West Virginia there was no raise for four years — even as the legislatures in those states gave big tax cuts to the oil and gas industries. In Arizona, state funding for schools, adjusted for inflation, had plunged 36.6 percent since 2008, the largest drop of any state. Though not a poor state, Arizona ranked 49th in spending per student, and its school counselors had an average caseload of 924 students, the highest in the nation.

Oklahoma and Arizona teachers clamored for higher pay, but they also demanded that the legislature restore hundreds of millions of dollars in school funding. In Los Angeles, the focus on bargaining for the common good was far more front and center. The L.A. strike was hardly about pay — when the settlement was announced Tuesday, the teachers accepted the same 6 percent raise that the district had offered before the strike began. The union, knowing that many students were poor, made gains that were mainly for the kids: more nurses, librarians and school counselors; and measures to provide more green space for schools, cut standardized testing in half and curtail the random searches that students detest.

Bargaining for the common good isn’t just an effective way to help students and schools, it’s also a smart strategy when unions are weak (and often derided as selfish). It’s a way to win allies so that union and community, together, can leverage their power.

It’s harder for private-sector unions to bargain for the common good, but the Marriott strike showed that private-sector workers can also win public support. The leaders of Unite Here, the hotel workers union, adopted the slogan “One Job Should Be Enough” because they knew it would win support and because it framed a problem facing millions of workers: Their main job pays too little to support themselves and their families.

D. Taylor, Unite Here’s president, told me that with the economy strong and many unions feeling beaten down, it was time for labor to engage in more strikes, to flex its muscle, to show what unions can achieve. He said: “It was important to restore the strike to the arsenal of the labor movement. If you’re in a fight against powerful forces, why are you taking tactics off the table?”

The hotel workers made impressive strides. Marriott housekeepers in San Diego won raises of 40 percent over four years (to $20 an hour from $14.25), while Marriott workers in Boston won a 20 percent raise over 4½ years, a 37 percent increase in pension contributions, and six weeks of paid maternity leave.

Success breeds success. So don’t be surprised if we see more bargaining for the common good, and more hotel and teacher strikes. Teacher walkouts are already threatened in Oakland, Denver and Virginia. A recent MIT study found that 46 percent of nonunion workers said they would like to join a union, and for labor, one happy result of the new wave of militancy is that it just might inspire more workers to unionize.