Students and Respect

Do you have a student who does not show you respect?  I come from a background in which students were taught to respect teachers.  Unfortunately, I'm not sure that's the case anymore.  Last year, my husband and I had a foster son, who had been homeless for 6 months prior to living with us.  His perspective was totally different.  He believed that, until a teacher showed him respect, he should not show respect to a teacher.  That was a real challenge for me and his teachers.  But  between us working with him at home, and the teachers understanding the issue and working with him, things were ok.  They weren't great, and they never became great except with two teachers, but they were acceptable.  How would you respond to a student who feels this way?