As your structure for managing behaviour develops, keep parents updated. Write a letter home explaining the rules, rewards and sanctions and detailing some of the new strategies that are having an impact. The conversations that you have with individual parents will start to have a shared context.
Parents will understand your interventions are fair and be more inclined to support your decisions.
Some parents, who are searching for ideas themselves will begin adapting strategies for the home.
Your first communication with parents will be a positive one, leaving the door open to discuss concerns about their child in the future.