Teacher protests are spreading like a cold in a kindergarten classroom.

After West Virginia educators' nine-day strike ended in a resounding labor victory last month that secured 5 percent pay raises, teachers in several more red states launched walkouts and rallied at state capitols this week.

Oklahoma's public schools remained closed on Tuesday as teachers held a massive rally at the state Capitol, lobbying legislators to increase funding for public schools. Teachers there have spoken about donating plasma and working second jobs to make ends meet. 

In Kentucky, thousands of teachers are spending their spring break rallying at the Capitol. Some schools that aren't on break were closed Monday and Tuesday. Teachers there are protesting a bill they say would cut their pensions. 

And teachers are threatening to strike in Arizona if they don’t get a 20 percent pay raise. So far, Republican Gov. Doug Ducey has said he will not give in to their demands and reiterated his plans to cut state taxes.

In all these states, teachers are among the lowest-paid in the country -- the average salary is just $44,921 in Oklahoma. These states also have relatively weak labor protection laws.

In West Virginia, collective bargaining is outright banned. In Arizona and Kentucky, there are no statutes allowing for teachers’ right to collectively bargain. Oklahoma teachers do have collective bargaining rights, but like the other states, their union lacks wide influence.

All four are “right-to-work” states, meaning employees aren't forced to pay union dues but can still reap the benefits of union-negotiated contracts. Where right-to-work laws exist, union membership is generally lower. In Michigan, for example, 14.4 percent of the workforce belonged to a union in 2016 -- down from about 20 percent at the start of the decade. The state passed a right-to-work law in 2013.

All four states also technically outlaw public-sector strikes.

Many labor experts believe weak labor laws -- such as the right to work and the lack of collective bargaining rights -- lead to lower salaries, eventually generating enough unrest for strikes to happen.

But a new study from Stanford University suggests this alleged causation, while intuitive, is a myth. 

“People think collective bargaining rights lead to ballooning public expenses and higher pay [for public employees],” says Agustina Paglayan, a fellow at the Center for Global Development and author of the study. “But that ignores that states that have collective bargaining rights were already spending more on education even before those rights [were instituted].”

According to Paglayan’s study, in 1990, teacher salaries were 18 percent higher in collective bargaining states. But as far back as 1959 -- before any state instituted collective bargaining rights --teacher salaries were still 18 percent higher in states that would eventually come to have these rights.

“This is, in part, because they’re more liberal and wealthier,” Paglayan says. “Often, red states are states that have historically paid their teachers little.”

Paglayan says she found no evidence that collective bargaining had a measurable effect on teacher salaries or education funding. She argues that's partially because so many states that have enacted these laws -- 19 of 33 -- also made striking illegal and subject to penalties, such as taking away two days of pay for every day of a strike. Without the ability to strike, unions lose their leverage in collective bargaining negotiations.

But the strikes in these Republican states point to a potentially counterintuitive reality: Weak labor laws don’t necessarily halt labor movements -- and may even help facilitate them. 

In the states currently striking, strikes are technically illegal and can cost a teacher his or her job. But, Paglayan says, “teachers know that will never happen. They can’t fire every teacher in the state." 

"The teachers unions [in the striking states] are not especially strong, compared to most other states on the coast, for example. And it’s very interesting that we’re getting these sort of wildcat, organized, Facebook-facilitated strikes in a way we’ve never seen before," says Nat Malkus, director of education policy at the conservative American Enterprise Institute. "What does it say about this situation that we’re seeing workers get a ton of traction without, or even in spite of, the unions?"

At a time when unions' strength could be significantly dampened if the U.S. Supreme Court rules as expected this year and allows public-sector workers to opt out of paying union fees, these strikes could be a good omen for worried public employees.