The state Department of Education has given each of Maine’s 600 public schools a letter grade, from A to F, and Wednesday is the day those rankings will be made public.

Just as an individual child’s report card is designed to give parents an indicator of that student’s progress, school grades — at least as touted by state education officials — are meant to provide a community with a benchmark of their school’s success.

The goal is to offer “a snapshot of where their school is at,” an Education Department spokesman told the Press Herald. But these snapshots leave more out of the picture than they include.

A system that assigns each school a single letter grade is hardly capable of reflecting the mix of elements that affect student performance, including community poverty, school funding and access to early childhood education. This approach doesn’t tackle the causes of low student success; it just records the symptoms.

Factor in a chief executive who consistently disparages public school educators and administrators — “If you want a good education, go to a private school,” Gov. LePage said last fall — and the chances of positive change are slim to none.

The A-F system assesses each school based largely on its students’ performance on standardized tests — on which students from poor neighborhoods or communities consistently lag their peers from wealthier areas. Schools with higher standardized test scores are likely to be in communities where per capita income is relatively high. So don’t expect to see many surprises on the list of schools with A or B rankings.

The lower-scoring schools, meanwhile, will have few resources to help their students catch up.

The Department of Education has all of $3 million set aside to help schools develop improvement plans, but this allocation hardly makes up for the LePage administration’s failure to fund education adequately. (Neither Gov. LePage nor his predecessor, John Baldacci, has ever carried out a 2004 voter mandate for the state to fund 55 percent of the cost of education.)

Under Gov. LePage, preschool and child care spending also has taken a hit, leaving students from low-income families at a disadvantage. These youngsters need the boost that early childhood education can give. Without it, they likely will start kindergarten less prepared than others. And they don’t have a lot of time to catch up: Research shows that youngsters have only a few years to develop the basic skills needed for academic success.

The A-F ranking system won’t tell Mainers anything they’re not aware of already. They know that schools in poor communities are hurting; they also know that the state isn’t willing to use a lot of its resources to help out. To demand progress under these circumstances is to give a test nobody should have to take.