This question has concern with an individual capacity of learning and hence it is the most debatable question among parents, tutors and students. There is no right or wrong answer as there are no clear cut rules formed. Often it is said that number of hours spent on homework help students to get the better academic achievement. But this does not work with all the students.
Each child has a distinct and unique way doing things. The tutors and parents should understand the actual purpose of homework. The time spend in doing homework should serve the purpose of homework and not become burdens that develop anxiety and frustration. Take homework as an extension of activities that goes in the school which gives practice and enrich students with the lessons that they have discussed during the day.
Young age students should spend less hours doing homework as they require time to play and cultivate hobbies that helps overall growth. While older students should spend a couple of hours more with the reason that each primary subject is learnt much more in detail.
For younger students, Math tutor online typically spends less than hour doing homework that gets completed in about 15-20 minutes. While they spend 45-60 minutes for middle class and high school students which may last longer more than an hour to complete complex problem statements.
Physics and Chemistry are the subjects learnt in high school and college level. Typically, Physics tutoring and Chemistry tutoring spend at least one hour to complete each set of homework in high school grade. The college students should spend equal hours on homework as that of spending learning Physics and Chemistry in their class.
However, the number of hours purely depends on age, grade level, kind of school you attend and number of classes you are taking.