You're in high school, and as a young person you should have more energy than most people. Take inventory of the other factors or conditions that might tell you why you feel this way:
1) Do you regularly get 7 - 8 hours of sleep?
2) Do you sleep normal hours (not going to bed super late or sleeping super late?)
3) Is your weight appropriate for your age and height?
4) Do you exercise?
5) Do you ever drink alcohol or use drugs?
6) Have you been to a doctor?
Just to name a few. Ask yourself these questions and be honest with yourself when you answer. If you still can't narrow down what is making you fatigued, by all means, see a physician and at least tell your parents.
Sometimes hormone imbalance and, of course, depression cause a feeling of fatigue, so the advice of seeing a physician is indeed wise. Other than a medical problem, having eaten too many sugary foods often cause a person to feel tired, so eating correctly and--by all means!--getting aerobic exercise such as walking or jogging will increase energy in a person, not to mention helping with one's mental well-being.
In my opinion, the only way to boost your energy is to live an overall more healthy lifestyle. I do not believe that you can take any supplements (like ginseng, which many people advocate) that will give you some automatic boost.
I believe that you boost your energy by eating properly (balanced diet, not too much meat, eat at proper times) and by getting enough sleep and exercise.
You need to see your doctor first and if he says that your health is in a good condition, you can use a natural remedy such rosehip syrup.
The minerals found in rosehyp make this syrup an excellent tonic for you. You can prepare yourself the syrup and you need: 200 grams of mashed rosehyp , 2l of water and 300 grams of sugar. You put all the ingredients together and you'll boil them.
The syrup can be kept in refrigerator and you have to take about 3 spoons daily, about a month, to feel energized.