Test-taking is never thought of as easy, but there are some people who really have a problem with it to a point where even if they know the information, they aren’t able to get a good grade on the test. You can help these types of teens by finding their specific cause and dealing with it.
Start by getting your teen on board. Talk to them and begin trying new things to create new study habits. Remember, high school is much different than middle school or elementary school. The problem could be in the new way your teen is learning at school. Also, make sure you are not the problem.
Assess your teen’s test-taking anxiety. Are there other 'stressors' in that classroom that can be dealt with? Tone them down as much as possible.
If you’ve done what you can at home and nothing has worked, talk to the school. Meet with the teachers and get ideas. Talk with the guidance office, they can help.