Michigan has wrestled for too many years over how to rate its schools. Thursday, the state Board of Education finally should launch an accreditation system that gives a letter grade, like a report card, to every public school.

This first step to helping ailing schools is a far better system than simply ranking schools by their MEAP scores. Those scores still will count, as about a third of the final grade, but another third is based on year-to-year improvement. A final third covers structural basics that make a school good, from parent involvement to academic planning.

Student improvement and support can show a lot more about a school's quality than a one-shot annual test. Where they exist, good scores usually follow. But some schools with mediocre or worse test scores may get decent final grades because they continuously show improvement. At the other end, some schools with excellent test scores may have big gaps in planning.

The results will draw complaints, especially from communities that believe their schools rate an A but don't get one. The state board needs to put together a strong information campaign, and lean on the schools to explain the plan thoroughly to parents and the community, long before the first school report cards arrive. Next fall is the goal.

This system will give all schools an honest evaluation, and it's particularly important to have the courage to identify the schools that let children down.

Failed schools need either massive intervention to get students learning, or they need to be closed. The state board plans to intervene, using money from the federal No Child Left Behind program -- assuming it comes. Other schools may have the occasional bruised ego, but this is really all about boosting opportunity for children who otherwise may have none.