The effects of lead on children are far-reaching: it can cause both health problems and challenges in school, driving test scores down and suspension rates up.

Now, a new study says there’s a lot that can be done about it — even for kids who have already been exposed to the chemical, which was common in paint until the late 1970s. Straightforward efforts, like making sure kids get nutritional help and aren’t exposed to any more lead, can boost student learning and cause substantial decreases in suspensions, absences, and crime rates.

The research underscores how factors outside schools’ control can profoundly influence academic outcomes.

The peer-reviewed research focuses on Charlotte, North Carolina in the 1990s, where young children who were found to have high levels of lead in their blood were given a battery of treatments, depending on the severity of their case. They included making sure someone was coordinating efforts to reduce students’ lead exposure and monitor their health, providing environmental and nutritional information, and a doctor’s evaluation.

Researchers Stephen Billings and Kevin Schnepel compared kids who got treatment to those kids who had relatively high levels of lead in the blood but didn’t get the extra help because their levels fell just short.

Getting that help seemed to moderately increase test scores in both elementary and middle school grades. Other effects were even more dramatic: Treated students were suspended six fewer days between sixth and 10th grades, and they were absent 10 fewer days.

The students who got the treatment were also much less likely to be cited for committing a crime in school. The chances of being arrested for a violent crime as a teenager fell from about 12 percent to nearly 4 percent.

Billings, of the University of Colorado, said those findings echo other research on the dangers of lead. “You see these effects tend to be hitting these behavioral outcomes more than anything else,” he said. “Lead impacts impulse control and things that are really important for not losing your temper and getting into altercations.”

Strikingly, as Charlotte students’ lead levels increased, their outcomes tended to get worse and worse — except at the point at which treatment began.

The kids who received the treatment were disproportionately black, male, and from low-income families. The gains from the program seemed to get bigger over time as students progressed through school.

These are large, statistically significant effects, though the number of students studied — a few hundred — is quite small and the results might not generalize to other contexts. “In different cities, different counties, different states, they might do a lot more, they might do a lot less,” Billings said.

The program also did not come cheap. The study estimates it cost over $5,000 per child at the time, paid for in part by local agencies. But quantifying the benefits — through higher test scores boosting future wages and lower crime saving money on prisons and law enforcement — suggests the expense was well worth it.

Although the findings are based on data from a few decades ago, the results remain relevant. The lead in the water of Flint, Michigan may have affected tens of thousands of children since 2014, and there have been elevated levels of lead in the drinking water in schools found in a number of districts recently, including Newark and New York City.

Lead poisoning has declined substantially in recent years, but as of 2014, over 4 percent of children had elevated levels of lead in their blood, according to the Center for Disease Control.  That may be a significant underestimate because of how the agency tracks data.

A 2016 Reuters investigation found that although poor children who receive Medicaid are supposed to be tested for lead, the majority aren’t.

Billings sees the study as part of a line of research showing how investing in programs helping young children has long-term benefits.

“We’re silly not to spend a good amount of money on that because we will save multiple dollars later on,” he said. “But it seems to be politically tough to get people to have that time horizon.”