HOUSTON -

Twenty Houston ISD teachers have been reassigned after the district says an independent investigation uncovered possible student testing irregularities at two elementary schools last year.

HISD says it happened during the 2012-13 school year at Jefferson Elementary School and Atherton Elementary School and that teachers under investigation have been reassigned to non-classroom duties within the district.

Eleven teachers from Jefferson Elementary and four teachers at Atherton Elementary School have been reassigned. In addition, five teachers who taught at Jefferson Elementary during the 2012-13 school year, but who are currently teaching at other HISD campuses, have also been reassigned as part of this investigation.

"Testing helps the district measure the degree to which students are learning," said HISD Superintendent Terry Grier. "When the district receives information that the integrity of the state's testing process might have been compromised, it's important that a thorough investigation is conducted. Throughout this process, our top priority is to ensure that learning is not disrupted for any student."

"I really think this is HISD trying to bring down the school," said mother, Maria Ramirez.

The staff representative at the Houston Federation of Teachers union says the teachers strongly deny the allegations.

"Absolutely," said HFT staff Representative Corina Ortiz. "And the one thing is, they have no information, no specifics about why or what the district is looking for."

HISD says the investigation is ongoing and, at this time, none of the 20 teachers have been found guilty.

Four of the teachers were at Atherton. The other 16 were current and former teachers at Jefferson. Parents we spoke to there are backing the teachers and are concerned for their children.

"I really don't think that they're looking at my kids' education here," said Ramirez Sanchez. "You know I really do not believe the allegations."

According to the district, depending upon the final results of the investigation, the 20 teachers involved will either return to their classrooms or a permanent replacement will be found.