First of all, let me assure you that music isn't only for those who can play an instrument wonderfully. Even if you want to focus on music theory, reading music, or even chord theory, there's plenty of time to practice in class and outside of class. The reason why music is so good for your brain is that it stimulates it and helps you learn things in ways most people don't always think about. It's all about practice and taking the time to really focus on learning.
When I say "taking time" I mean real hard work. Music doesn't need to be played on a piano or violin or in a band - any piece of music will do. You should make a conscious effort to spend some time each day playing - no more TV, computer, games, reading, etc. This applies to both school work and your personal life.
What you're trying to do is get your brain working at full speed. That means you need to be doing lots of long, slow-motion exercises. These types of exercises to build up your strength and your motor skills and they'll help you do better on your tests. They're also great for your body because you'll be strengthening your heart and your lungs.
Another question I hear a lot is, "If studying is so good, why do people do other things?" There are several reasons, but one of the biggest contributing factors is actually having fun while you study. Make sure you have a few hobbies and activities that you enjoy doing and you'll do much better. I like to paint - it's relaxing and I can take a break and do painting while listening to music - any kind will do.
Another question often asked is, "Do I need to learn a certain amount of instruments in order to study music?" Actually, no, you don't. Just take a look at any orchestra. Even if they play a few instruments, most of them play all of them. The reason is not only do they love their musical instrument, but they love to study music as well - it's part of their lives.
Studying music is just a matter of sitting down and thinking about it. Practice every chance you get. Spend an hour a day practicing, if you can afford to do that. Music is a great stress reliever, but you must remember to focus or else your brain will start to wander. If you're studying music for any reason, try to find a quiet place and try to make studying into an actual game - like crossword or word puzzles.
The truth is music is a great stress reliever, but it's also a wonderful way to relax while studying. Studies have shown that students who perform better tend to do better on their exams. So, if that's what you want - a good night's sleep and a little bit of extra stress relief - playing some good music is definitely a great way to go. Good luck!
As for is music good for studying? If you're doing an exam, the answer might be yes. However, that's not necessarily the most helpful answer. Exams are usually pretty hard work. A good night's sleep, a healthy diet and some good music can make studying for that exam a lot easier.
Another example - if you're preparing for any sort of test, the answer might well be no. However, it's probably not a good idea to bring heavy classical music into the exam room. Instead, bring some contemporary music or jazz if you want some study time during the day.