Teachers are revolting — striking for better pay and improved school funding. Last month, the nation watched an unprecedented nine-day statewide strike in West Virginia, which ended only when the legislature passed — and the governor signed — a 5 percent raise for all teachers.

Last week, threatened with a similar strike, the Oklahoma legislature offered a raise and increased school funding — but not enough to stop teachers from striking. Arizona and Kentucky teachers have organized sickouts and rallied at their state capitols, with similar demands. Teachers in these red states are among the worst-paid in the country.

Why the low pay and unrest among public school teachers across conservative states?

Some observers believe weak labor rights are why teachers in these states are among the lowest-paid. These states don’t require local school districts to bargain collectively with teacher unions — and weaker labor rights leave teachers worse off. If only these states mandated bargaining with the unions, this argument goes, teacher salaries would be higher and there would be fewer reasons to strike.

But that’s a myth. My new research shows collective bargaining rarely leads to higher teacher salaries and more education spending. Teachers in red states are striking because of their low pay — but that is not because their labor rights are weak. The problem is they teach in states that have historically spent little on education.

Teachers and education advocates march outside the state capitol in Phoenix to protest low teacher pay and school funding on March 28. (Ross D. Franklin/AP)

Here’s how I did my research:

Before the 1960s, virtually all U.S. states prohibited collective bargaining for teachers and other public employees. Beginning with Wisconsin in 1959, 33 states in total over the next 20 years — mostly outside the South — and the District of Columbia repealed this prohibition and required districts to bargain with teacher unions. In the remaining states, 10 states allowed but did not require bargaining with unions, and seven states, mainly in the South, prohibited it.

That pattern remained stable until 2011, when Republicans in Wisconsin and 10 other states passed laws that cut back teachers’ collective bargaining rights, promising this would help reduce public deficits.

Since collective bargaining rights for teachers did not emerge until the 1960s, we can look at the difference between those states that did and did not mandate collective bargaining to see whether these rights affected teacher salaries, employment and education spending.

To quantify the effect of mandatory collective bargaining with teachers, I tracked teacher salaries, the number of teachers hired, public spending on education, and spending on non-wage things such as pensions and health benefits across all 50 states from 1919 to the present.

Here are three things I found, and one implication for policymakers.

1. Teachers got collective bargaining rights in states that already paid teachers well.

By 1990, teacher salaries were 19 percent higher in states with mandatory collective bargaining than in states without. But that is not because of mandatory collective bargaining. The states that adopted these labor laws were historically wealthier and more liberal. They already spent more on education, even before mandating collective bargaining.

The gap in teacher salaries and education spending that we see today between states with and without mandatory bargaining already existed in 1919 — long before the rise of teacher unions.

2. Mandatory collective bargaining didn’t increase teacher pay or education spending.

After states passed these bargaining laws during the 1960s and 1970s, there was a sharp rise in the share of teachers covered by collective bargaining agreements, in teacher union membership, and in teachers’ political engagement.

What didn’t increase more were teacher salaries, the number of teachers hired, or public spending on education.

As you can see in the figure below, after some states mandated collective bargaining and others didn’t, the teacher salary gap between those two groups of states stayed more or less the same. Between 1959 and 2000, teacher salaries increased by 43 percent in states that introduced mandatory bargaining and by 47 percent in states that did not. The same thing goes for education spending and the number of teachers per student.

It is not the requirement to bargain with unions that makes the difference in how much governments spend on education and teachers.

3. It’s tougher to strike in states that mandate bargaining with teachers.

Public-sector strikes became a major problem in the 1960s. And that is a key reason that, in most states, legislators decided to grant collective bargaining rights to public employees. Both Democrats and Republicans wanted to avert public-sector strikes — and they thought collective bargaining rights would help pacify upset public employees.

But those states’ legislatures didn’t just grant collective bargaining rights to teachers. In 19 of the 33 states that introduced mandatory collective bargaining with teachers, the new state labor laws heavily penalized teachers and unions that went out on strike. Striking meant teachers would lose pay, unions would be fined, existing collective bargaining agreements would be suspended, unions would lose the automatic deduction of fees from districts’ payroll, and more.

Teachers and unions in these states paid a high price for the right to collective bargaining.

Red-state teachers have less to lose from going on strike.

Teachers in red states are striking because of their low pay — but that is not because their labor rights are weak. It is because those states have historically paid teachers poorly.

Labor laws do matter, though; they can make it easy or costly for teachers to strike. Teachers with weaker collective bargaining rights have much less to lose if they strike than teachers in most mandatory bargaining states, who would incur harsh monetary and organizational penalties.

Since the 1960s, mandatory collective bargaining laws have not only helped maintain peace in public-sector labor relations — they also haven’t caused governments to spend more on teachers and schools. Ironically, conservative lawmakers who cut back these laws could inadvertently cause even more public-sector strikes.

This season’s teacher strikes could be a sign of things to come.

Agustina S. Paglayan (@aspaglayan) is an incoming assistant professor of political science and public policy at the University of California at San Diego and a postdoctoral fellow at the Center for Global Development.

This post is based on a study funded by Stanford University and accepted for publication at the American Journal of Political Science.