Parent/Guardian Communication is vital in a classroom. They need to communicate multiple different things for their students. Such as birthdays, classroom events, school-wide events, field trips, behavior, report cards, etc.
Newsletters
Teachers can send home weekly newsletters on what was learned in the class that week to keep parents up to date.
Parent Conferences
Parent Conferences are a great way to talk in person with a parent/guardian. It's more personable, and can be very beneficial.