A child in public school spends something like 7 hours a day for 180 days a year attending school. And yet this is not even enough for them. Teachers demand not only the in-class time, but the child's time when he or she is at home in the form of homework assignments! Families spend so little time together as it is, and after school and work there may only be one or two hours of opportunity. Is this time really best spent on classroom assignments?
Of course, demanding the child's time even when away from school helps reinforce what I consider the most evil aspect of public schooling: replacing the home with the school as the center of the child's existence; replacing one's family and community with class-mates as the center of the child's social life.