There is no magic number of hours, quality of focus matters far more than total hours. For most school students, 4 to 6 hours of focused study a day including school is plenty, while serious competitive-exam aspirants may need 6 to 8 focused hours. But studying 10 distracted hours is worse than 4 focused ones.
What really counts is concentration. One hour of deep, distraction-free study beats three hours with your phone buzzing beside you. So instead of asking how many hours, ask how focused am I in the hours I study.
Match your hours to your goal. A Class 8 student does not need the same schedule as a Class 12 JEE aspirant. During normal school days, 2 to 3 hours of self-study after class is reasonable. Closer to exams, this naturally increases.
Example: A Class 12 student in Hyderabad preparing for boards might do 3 hours of focused self-study on a school day and 6 to 7 hours on weekends, using the Pomodoro method, that is study 25 to 50 minutes then break 5 to 10. This is sustainable for months, unlike 12-hour marathons that lead to burnout within a week.
Listen to your body and mind. If you cannot focus, a short break or a walk often restores more productivity than forcing yourself to sit longer.
One practical tip: Track focused hours, not seated hours. Use a simple timer and only count time when you were genuinely concentrating. Most students are shocked to find their 8 hours was really 3 focused ones, and fixing that changes everything.