It was the fifth state in recent weeks in which teachers have gathered in large numbers, at the statehouse and elsewhere, to call for money funding for education. Colorado, Kentucky, Oklahoma, and West Virginia teachers all took to the streets to publicize their calls for increases in funding or, in some cases, rollbacks of cuts. West Virginia teachers succeeded in getting a pay increase from the state legislature there; the same was true in Oklahoma, although teachers went back out on strike to demand an even larger increase before settling for the one they got.

In Phoenix, the crowd numbered in the tens of thousands, with teachers calling for a 20 percent raise in their own pay, an increase in pay for support staff, and about $1 billion more in education funding. Arizona teacher average salary is well below the national average.

The state's governor, Doug Ducey, has set out a plan for meeting the teachers' demands, but protest organizers say that the revenue projections needed to offset the salary increase (which included no increases in taxes) were too optimistic.

The Arizona Education Association said that it had no end date in mind for the teacher walkout; more than 840,000 students in more than 100 districts across the state did not go to school. The state's Department of Education said that the schoolchildren population was more than 1.1 million.

It was the second large public action taken by Arizona teachers. They recently staged "walk-ins," conducting before-school protests and then wearing Red for Ed shirts and buttons while they taught their students.

The crowd was markedly smaller in Denver but still involved teachers from 27 districts; all affected schools were closed for the day. Colorado lawmakers have already vowed the state's education funding increase since the 1930s, but teachers say it isn't enough.

Colorado is the odd state out in this collection. The other states are run by Republican-majority legislatures and have Republican governors. Colorado, by contrast, has a Democratic governor but a long history of abhorrence to new taxes, even if they are earmarked for kindergarten facilities; voters in the state rejected such a tax just four years ago. The state constitution has an amendment known as the Taxpayer's Bill of Rights that gives voters the final say on tax increases. As a result, part of the thrust of the Colorado teachers' protest is for a ballot initiative on this year's ballot to raise taxes on corporations in order to pay for a funding increase for education.