Wisconsin State Journal Editorial:

Wisconsin’s three-legged stool of school finance is wobbling and about to fall over.
The Legislature needs to prevent a terrible crash by rejecting the governor’s attempt to kick out the sturdiest leg of the system — the QEO, or “qualified economic offer,” which limits increases in teacher compensation.
Wisconsin’s system of paying for public schools has long been described as a three-legged stool. It’s designed to protect property taxpayers and the quality of K-12 education.
The three legs are:

Much more on the QEO and Wisconsin school revenue limits here.