Do you have your meals on time? When do you have your first meal of the day? If you skip breakfast, then you must focus on having a good breakfast early in the morning as it is the most important meal of the day. Having a good breakfast comprising of whole grain cereal/milk and fruit will boost your energy levels, improve concentration thereby enhancing your ability to perform well in academics. Also you must avoid eating junk food like burgers, french fries, pizzas, noodles as a part of regular diet. It is ok to partake of these foods once in a while but having them regularly displaces nutritious food from your diet. Nutrient deficiencies especially iron can contribute to anaemia which causes easy fatigue in school children. You must get your haemoglobin checked to see if it is normal. If you are anaemic, then that could be responsible for making you tired and affecting your school performance. Hope I have answered your query satisfactorily.