It's good to be concerned about taking a test. It's not good to get "test anxiety." This is excessive worry about doing well on a test and it can mean disaster for a student.
Students who suffer from test anxiety tend to worry about success in school, especially doing well on tests. They worry about the future, and are extremely self-critical. Instead of feeling challenged by the prospect of success, they become afraid of failure. This makes them anxious about tests and their own abilities. Ultimately, they become so worked up that they feel incompetent about the subject matter or the test.

It does not help to tell the child to relax, to think about something else, or stop worrying. But there are ways to reduce test anxiety. Encourage your child to do these things:

Space studying over days or weeks. (Real learning occurs through studying that takes place over a period of time.) Understand the information and relate it to what is already known. Review it more than once. (By doing this, the student should feel prepared at exam time.)
Don't "cram" the night before--cramming increases anxiety which interferes with clear thinking. Get a good night's sleep. Rest, exercise, and eating well are as important to test-taking as they are to other schoolwork.
Read the directions carefully when the teacher hands out the test. If you don't understand them, ask the teacher to explain.
Look quickly at the entire examination to see what types of questions are included (multiple choice, matching, true/ false, essay) and, if possible, the number of points for each. This will help you pace yourself.
If you don't know the answer to a question, skip it and go on. Don't waste time worrying about it. Mark it so you can identify it as unanswered. If you have time at the end of the exam, return to the unanswered question(s).
U.S. DEPARTMENT OF EDUCATION
OFFICE OF EDUCATIONAL RESEARCH AND IMPROVEMENT