A good preschool will encourage parent participation and may make requests throughout the school year for parents to volunteer. Take the opportunity to come into your child's classroom and interact. It will help your child see that you support their learning plus it will help you understand what your child is talking about when they get home.
A preschool should not push your child faster than they are developmentally ready to go. Not all children mature at the same age and some are simply not ready to sit and attend to academic tasks when they are three to five years of age. Take a good look at your child's maturity level if they are becoming anxious or stressed about attending preschool, they may just not yet be ready.