A high school senior in Florida claims she is being unfairly punished after showing a marked improvement the second time she took the college entrance exam. Now she worries she won't get into the school of her choice.

Kamilah Campbell, 18, thought she did everything she could to increase her SAT score from 900 to 1200. But then she received a letter from the testing company saying her score was invalid.

"They tell you that you need to practice and work and study to do better but then when you do better they question it," she said.

Kamilah Campbell. CBS News

The Educational Testing Service, which oversees testing for college entrance exams, told Campbell that her score is under review because of discrepancies on her answer key.

"Because it improved for over 300 points, so they're saying I improved basically too much and that's skeptical for them," Campbell said.

She credits her more than 300 point improvement with months of studying, tutors and a free online SAT prep program.

"They are not looking at it as if, 'Maybe she focused and dedicated herself to passing this test,'" Campbell said.

Now she said she missed the deadline to apply to her first choice, Florida State University, and can't apply for SAT score-based scholarships. Attorney Benjamin Crump is considering a lawsuit.

"We intend to fight for the legitimacy of Kamila's test scores," he said.

Despite the setback, Campbell is undeterred.

"I am proud of myself and I need my scores released," she said.

Educational Testing Services said they don't cancel scores based solely on a point increase. They said other factors, which they won't disclose, are taken into account. If it doesn't validate the score after its review, Campbell will have to retake the test.