You seem to keep failing your tests probably because don't understand most of what you study. There is a big difference between reading and understanding. Make sure that you understand what you read by grasping the concept. Ask your teacher or tutor for help if you find any topic difficult.
You need to understand the concept and not just memorize the facts. You must know why it is so. And also make sure to pay attention in class rather than studying last minute. Also keep the knowledge long- term