I volunteered all the time when my daughter was in elementary school. Now that she is starting middle school, she has asked me not to help out at her school. I am a stay at home mom and I'd really like to help out.
Volunteering is one of the best ways to stay on top of what's happening around school. As a compromise you could help out in the office or media center instead of in your daughter's classes. This way you can be involved while still fostering the independence that your daughter is asking you for. If that's not enough for you, get involved in some of your PTA's projects.