Back-to-school season may have New York City students worrying about more than homework this fall.

The city’s education department revealed Tuesday that it hasn’t managed to keep lead-contaminated water out of all the city’s public schools, the New York Times reports. 

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 This presents a huge liability, considering young children who come into contact with even the smallest amount of lead can suffer serious brain damage, as was exposed by the Flint, Michigan, water crisis. 

The education department said it has made progress in removing lead from the public school system over the last year, but there are still more than 1,100 water fixtures in New York City with dangerously elevated levels above the Environmental Protection Agency’s standards. Researchers found lead in the water coming out of drinking fountains, bathroom faucets, and sinks from 12,457 different sources across 1,500 schools between 2016 and 2017. 

While 91% of tainted water fixtures in schools have been fixed, that leaves 1,165 to go.

Last year the crisis looked a lot worse. Most public city schools, 83%, had at least one water fixture with elevated lead levels. Now the number is down to 25%, based on inspections conducted from the fall of 2017 to fall of 2018.

Dr. Oxiris Barbot, New York City’s health commissioner, appeared to tiptoe around the issue in a statement.

“Everyone should know that New York City’s drinking water remains the best choice for staying hydrated and an excellent alternative to sugary beverages,” she said Tuesday, according to the Times. 

The city is, however, committed to make up for how it previously neglected lead contamination. By 2020, schools will be checked for lead twice a year. 

In the meantime, students are being warned to stand clear of contaminated water. About 730 fixtures with elevated levels are explicitly marked for handwashing only, and the other 435 fixtures aren’t running. 

Some children still have to worry about lead when they go home if they live in public housing. In June, the city was charged for covering up lead paint violations in housing projects.

New York is only one US city struggling to provide clean drinking water in school systems. In August, Detroit schools had to shut off water faucets after finding unsafe lead and copper levels.