Nearly 200 water faucets in Oakland public schools had levels of lead that exceeded district standards, sparking outrage among staff who criticized district officials this week for failing to immediately notify school communities about results found earlier this summer and spring. It’s unclear how long students were exposed to the tainted taps.

Out of the 1,083 faucets and fountains tested, nearly 83% fell below the district’s limit of 5 parts per billion, or ppb, meaning they were safe, but 17% were above the limit. Federal standards are more lenient than Oakland’s standards, at 15 parts per billion, but 70 taps in the districts also failed to meet that requirement, in some cases by a wide margin.