Self Doubt Leads to School Problems

The brunette twins's ability to doubt herself is now creating problems with her school work. Her math grades have been fluctuating wildly. One day she's perfect. The next day she misses a lot of answers.
The problem is she's not getting marked down because she's not getting the right answer. She's getting marked down because she's not even answering the questions. The math assessments are timed. She works herself into a complete panic because the tests are timed and freezes. She said, "I get a funny bad feeling in my stomach and can't think."
We don't know how to help her manage this anxiety. She knows the answers when she's doing the work at home or in the classroom. It's the timing that causes the problems.
She works herself into a near panic attack whenever she has to take a math test. We all know how much schools like to test students. This is a problem that could have long-lasting effects on her academic opportunities if we don't figure out how to manage it -- and quickly.