Teachers in Oklahoma are planning to walk out of the classroom next week to demand a salary increase, part of a wave of teacher activism across the country from Arizona to West Virginia.

Why this matters: Teachers are protesting for pay raises and better benefits. In most states their salaries haven't kept pace with inflation.

Expand chart Data: National Center for Education Statistics, The Council for Community and Economic Research; Note: Estimated average annual salary of teachers in public elementary and secondary schools, adjusted for inflation; Chart: Andrew Witherspoon/Axios

The teachers in Oklahoma, who are planning to walk out on April 2 if no agreement is reached with the state, are following teachers in West Virginia who walked out of the classroom for nine days before finally getting state legislators to authorize a pay raise. Teachers in Denver and Arizona have also discussed walking out of the classroom for better funding and pay raises. Teachers in Kentucky had a sick-out on March 30.