Many children do not perform well in their studies, and even become rebellious when forced to study. Among those who do not study properly, the most common issues (presuming there is no developmental disability) are:
Environmental factors: too many distractions, TV, social media, peer pressure, addictions, does not like the school atmosphere, feels subject is of no use, bullying
Inability to comprehend: Slow learners, dyslexia, fundamentals are weak since previous year, does not like teacher, sitting too far back in class, language difficulties
Home: Strict or too lenient parenting, parental expectations, comparison, competition, boredom and loss of motivation since he feels he already knows enough
Emotional/physical issues: Anxiety or stress, exam fear, mood swings and anger, past failures, bad relationships, sense of isolation and loneliness, self-esteem, poor eyesight, fatigue.
If the correct cause is not identified there is no point in pushing him or scolding him. He may not only not study, but also disturb others and create problems in class, become rebellious with parents, and get into bad company. Once the cause(s) is identified we can work out who can resolve each to what extent: parents, teachers, friends, counselors, special educators, doctors. With team effort most children can be encouraged to study well and achieve success.