Testing has found high levels of lead in water at 99 Chicago schools.

All had at least one sink or water fountain that had water with more lead than the federal Environmental Protection Agency’s so-called “action level” of 15 parts per billion, according to Chicago Public Schools officials.

At Onahan Elementary School, 6634 W. Raven St. in Norwood Park, high lead levels were found in four drinking fountains. School officials said they plan to re-test when classes resume because the water might have been turned off in the days before samples were collected, potentially compromising the results.

The school system began testing water this spring in the wake of the lead crisis in Flint, Mich. So far, laboratory results have come back for 263 of the city’s 500-plus schools, according to CPS, which announced the latest figures Friday night.

The results are posted online — at www.cps.edu/leadtesting — as they come in.

Exposure to lead is especially dangerous for young children, whose brain development can be impaired by even tiny levels of the metal, which they’re most often exposed from lead paint, though it also can leach into drinking water from lead pipes — whose installation was banned in Chicago in 1986.

CPS officials haven’t said how they plan to replace plumbing and fixtures that have caused high lead levels, focusing on the fact that a relatively small number of faucets or water fountains — 160 of 4,924 tested to date — had lead levels above the action level.