Hello dear It could be possible that in spite of 7-8 hours of sleep, you feel sleepy because that might not be a sound sleep. Your sleep might be a disturbed one which makes you feel tired and sleepy during the day as well. You can try meditating daily twice a a day to relax your mind (morning and one before sleeping). Try reducing your mental burden before sleeping to have sound sleep which in turn increases concentration. Also try avoiding distractions during the coaching class to increase your concentration.