Wow, that's a lot of worksheets!  Is the teacher using worksheets instead of textbooks?  Are worksheets the only thing your son's class does?  What I mean is, is there time built into their day to read books, go to centers, do simple experiments, explore or even recess?  Are all lessons follow up with a worksheet?  Some worksheets are more purposefully than others.

I would talk with other parents at the school of all grade levels.  Ask them if this is typical of all of the teachers.  If it is, it might be time for you to become an active member in the Parent/Teacher Association.  If it is only this particular teacher, I would talk with the teacher first to hear the rationale.  If you still feel something is wrong, make an appointment to talk to the administration.

Try to have some fun with your child at home when it comes to math.  There are many activities and games you can play that involve math skills.  You don't want him to lose that motivation.  For ideas check out Education.com's activities - http://www.education.com/activity/