Continuing concerns

Many of my students are continuing to struggle with their grade in both the Earth and Life Science courses.  The reason their grades are so low is because they don't turn in the assigned homework.  Missing work in my classroom is given a grade of zero.  This may seem harsh, but I believe that part of my job is to teach your child to become a responsible young adult.  Their responsibility is to complete the homework and turn it in on time, not when they "get around to it".  Someday your child will have a job, and their employer isn't going to tolerate work assignments being done whenever your child gets around to it.  Behavior like this will get them fired; I'm trying to establish good behavior for their future.