Over the years public schools have provided less and less for "free" education.  As a child my parents purchased very little for my sisters and I to attend school and paid a small $10 fee.  Now parents have to buy most if not all supplies and pay book fees and other fees that are ambiguous at best.  Low income families have a difficult enough time and particularly in the current economy.  School fees add to the stress of providing for day to day needs of the household.