Your mind is wandering because of the effect of the male sex hormone, testosterone. This will clear up in exactly two years but you must conduct yourself well. Meet with a counselor and get some help. You must learn to study smart than to study hard and too much. Academic pressures nowadays are very high and many kids are succumbing to it in many stress
-related ways. It is really important to bring in some efficiently to study and reduce the pressure. With regard to memory, it is very important that your brain and body is rested well to be able to recall whatever is required, rather comfortably. So, catch a good 8 hours of sleep every night. Puzzles pose problems to the brain that help it to use new pathways and neurons, which give the brain considerable exercise. It taxes the left brain to use logic to solve the myriad possibilities which other activities do not stimulate. Crosswords are excellent for vocabulary learning and use. Jigsaws and Rubik cube stimulate different permutations to finally settle on the most likely one. Picture completion and anagrams help approach problem solving from several angles. Do Sudoku, and memory co-relation activities and skills. Have a good breakfast of more proteins, meditate often, remain free of stress, eat a lot of fiber (whole grains, fruits and vegetables), nuts, avocado, eat dark chocolate, do Yoga meditation
exercises, etc. You need to check out, if you are stronger visual or auditory. The visual is a better mode than the auditory. However, if you combine the two modes, you will get the best concentration. Have a special place of learning, which should be well lit, with soft painted walls, well-ventilated, with no distractions. When you get bored, study by writing. If you repeat learning at least five to seven times, you will apparently remember for a longer time. Sit comfortably but do not slouch. The reading material should be of a fairly large print. Study at small intervals of about 40 minutes and then take a break or change the subject. Short-term memory is a faculty of the left brain, and long-term memory is a feature of the right brain. When people are stressed, they tend to favor the right brain and abandon the left brain, where short-term memory resides. So, it is really very simple: deal with the stress and activate left brain functions. Here are a few suggestions to activate left brain function: shut your left nostril and breathe, move your eyes from right to left and vice versa for at least half a minute at a time, and do callisthenic exercises with some form of counting, regularly. There are some memory enhancing techniques and study methods that your teacher will be able to guide you with. You may also meet with a counselor to take care of the stress related emotions, and then you will fare better too.