HOUSTON – When Houston Independent School District announced plans for district-wide water testing last month, the district was quick to point out an early round of lead testing showed no problems in five of the district’s buildings.

But KHOU 11 Investigates has uncovered a second round of testing that shows high levels of lead inside one of HISD’s high schools.

In March, as concerns about lead in drinking water spread nationwide, the school district says it decided to test the water in five randomly selected schools.

Records confirm that the water tested inside Wharton Dual Language Academy, Hogg Middle School, Henderson Elementary, Mickey Leland College Preparatory Academy and McReynolds Middle School was all within the accepted range of lead according to federal standards.

Those are the test results the district referred to. But through open records requests, KHOU 11 Investigates discovered that in April, HISD conducted additional testing at seven more schools.

Related: Parents push for bottled water as HISD tests for lead

The schools were all former North Forest ISD buildings that Houston absorbed in 2013.

Tests found acceptable lead levels in the water at Hilliard Elementary, Forest Brook Middle, Thurgood Marshall Early Childhood Center, BC Elmore Elementary, Fonwood Elementary, and Shadydale Elementary Schools.

However, district records show one of three water samples taken from North Forest High School contained nearly three times the acceptable level of lead according to EPA standards.

Testing records show that sample came from one of the 63 year old building’s bathrooms.

A spokesman for HISD said four faucets believed to be the source of the lead were replaced inside North Forest High. However, he confirmed that no follow-up testing on the water occurred.

Instead, HISD says it will be re-tested as part of district-wide sampling this coming school year.

The EPA warns that children exposed to lead may experience delayed mental development, lower IQ levels, reduced attention spans and hyperactivity.

Because of the risk, Dr. Stan Spinner, Chief Medical Officer of Texas Children’s Pediatrics warns parents should not shrug off the high lead levels found.

“I would absolutely take it seriously,” Spinner told KHOU 11 Investigates. “We can't reverse the effects of what lead can do once it's in the body and once it's caused some damage. We can't fix that, so we would definitely want to be certain and I would want to be certain as a parent as well as pediatrician that our children are not being exposed to any kind of lead.”

Because experts are not sure how long a child needs to be exposed to lead before problems occur, Spinner says it’s important water be tested if there’s any chance of lead contamination.

“Lead’s a serious problem,” said Spinner. “So in our schools we should be certain it’s safe and in all drinking water wherever that is, I think we should be certain it’s safe. If there’s any indication of a problem like that, I would certainly be very cautious about it.”

Right now, there are no state or federal rules requiring schools hooked to municipal water supplies to conduct lead testing.