I also struggled with exams, but that's because my understanding was often shallow, due to a lack of effort to study and understand the material. I'm very suspicious of people that say they're smart, but can't perform on exams. That said, there's plenty of ways to structure things to avoid this. Have weekly, easy, pass / fail exams that ensure you've read the material at a basic level, or understood some basic concepts. Lab work. Presentations with live grilling from the professor to ensure you understand the topic.