Congratulations to Yarmouth High School, which led the state for a second straight year in math on standardized tests.

The state reports that 74.3 percent of Yarmouth students were at or above grade level this year, a slight improvement over last year, when 72.5 percent made the grade.

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But Yarmouth schools had a much lower score on another important test — 10.1 percent. That’s the percentage of students who qualify for free or reduced-price meals because their family income was less than $21,590 a year.

Yarmouth was not the only school to see such a big split.

In second place, Falmouth had 72.6 percent of its students working at or above grade level in math, and only 6.3 percent qualifying for assistance with meals. Third-place Greely High School in Cumberland finished with 62.3 percent at or above grade level, and 9.7 percent qualifying for assistance. At Cape Elizabeth, the numbers were 62.3 percent proficient and 5.3 percent needing help to buy food.

In other schools, there was a much different split. At Portland High School, for instance, 31.9 percent of students were proficient in math, while 55.3 percent qualified for free or reduced-price meals. At Lewiston High School, 17.4 percent were working at or above grade level in math, while 58.8 percent received assistance.

While the correlation is not perfect, it repeats itself up and down the state of Maine. A school’s percentage of students who come from poor families will fairly neatly predict how well that school will perform on standardized tests.

What inferences should we draw from that? Are poor kids bad at math? Have schools in wealthier towns found some new way to teach?

No. This illustrates, once again, that the stress of living in poverty makes it harder for children to come to school ready to learn.

You shouldn’t need statistics to figure it out.

It stands to reason that a child with a full belly would be better prepared for what comes at him at school than one who may not get enough nutritious food at home. Or that a child who can’t stay home when he’s sick because his mother has to work is more likely than one who can stay home to develop a chronic condition that interferes with learning. Or that children who constantly have to move because their family has trouble finding affordable housing will be less likely to ace a big exam than children who come from more stable homes.

That doesn’t mean that there aren’t exceptions. Everyone knows a story about a poor kid who overcame a tough upbringing and excelled, or a middle-class one who failed to thrive despite having all the advantages. Some school districts have found ways to get their students to punch above their weight on the tests. But you can’t ignore the overall trend.

These tests are measuring more than how much a student knows about algebra. They are also measuring what is happening to them after the last bell rings in the afternoon and the first one rings in the morning.

Hard work, tenacity, curiosity and creativity all contribute to success in school. But so do housing, health care and nutrition.

We can look at these scores and demand that teachers do a better job or that principals should be fired, but until we get serious about making sure that families have a chance to give their students a stable home, the inequality will not improve.