SAN ANTONIO -- Kailee Wegehaupt and Lindsey Terrill are advanced sixth-grade students at La Vernia Middle School. They are so proficient in math, both tested to skip sixth grade math. They enrolled in "Credit by Exam" through Texas Tech University. Students who score a 90 or above can skip a grade in the subject tested.

"It was really easy for me, and I learned most of the stuff in fifth grade," Lindsey said.

Kailee Wegehaupt was also confident she did well.

"It was pretty easy, and I didn't think I was going to get a bad grade or anything," Kailee said.

Kailee and Lindsey were shocked when the test results came back -- they got a 73 -- a failing grade.

Lindsey's mom, Debi Terrill, asked her daughter about it right away.

"It says you made a 73," Terrill told her daughter. But Lindsey responded, "Mom, I'm telling you I might have missed one. I did not make a 73."

Kailee's mom, Dee Wegehaupt, called the school right away. Wegehaupt said the school's first reaction was to question whether Kailee had just had a bad day.

"Did she have a game last night? And I told them, 'No, none of those things.' It just didn't make sense," Wegehaupt said.

Determined to get answers, they called Texas Tech and asked to see the exams.

"We can't let the tests go out from the school," Wegehaupt said Texas Tech told her.

So the mothers threatened to drive to the school to see the tests for themselves. That's when, they said, Texas Tech agreed to review the exams.

Two weeks later, after calling the school looking for answers, they were told the exams were reviewed and the results were sent to their school district. A few days later, they got those results.

"She had a 97. ... That is like a 23 point difference. I was flabbergasted!" Wegehaupt said. It turned out Kailee and Lindsey had actually scored a 97.

KSAT 12 NEWS contacted Texas Tech, but school officials said they would not discuss these particular cases or agree to an interview. In an e-mail, Michele Moskos, director of marketing, said, "All of our CBE's are graded by Texas certified instructors. ...Additionally, the College of Outreach and Distance Education undergoes regularly scheduled audits."

For Terrill and Wegehaupt, their persistence paid off. Now they warn other parents to pay attention and make sure their child's test results add up.

"If your child tells you, 'Mom, I know I had a better grade, I know I didn't make a 73,' then challenge," Terrill said.

Kailee and Lyndsey have maintained a 100 percent average in seventh-grade math.

Credit By Exam is based on state educational standards and depending on the school district is offered either through Texas Tech University or The University of Texas at Austin.