This can be very difficult as different families have differing values, expectations, and discipline systems.  The good news is that children can adapt.  Just because rules are one way at home, they can learn to behave a different way in school.  Don't say the parents or the family is wrong for what they do or how they disipline, but always be clear about "this is how we do things at school."  Set up the rules, expectations, and follow through with whatever you set up.  Even in school, this can vary from classroom to classroom.  Some teachers are very strict, others may be more laid back.  Set up the environment for your classroom within the rules and disiplinary structure set forth by the school, communicate clearly with your students, and don't be afraid to consult with administration if a student has an issue that you are having trouble coping with.  Communicate these same expectations with parents if they have questions or concerns.  If the parents take exception with some of the policies and procedures, refer them to administration for further explanation.  

We wish you luck with this.  It can be very difficult to deal with these sorts of issues because of the many backrgounds, families, and cultures that have very differing views on discipline.  Keep your classroom consistent with school rules and be transperant with students and parents about this information.

Counselor, Dominic
Boys Town National Hotline-A resource for teen and parents
1-800-448-3000
www.parenting.org