You don't want to wait until report card time to realize that your child is struggling in school. Throughout the year, keep an eye out for these warning signs:
You'll notice these signs sooner if you participate in your child's education. Help her with her homework, or ask periodically if she needs a hand. Don't be overbearing, but do be proactive.
Most teachers will contact you first if they think your child needs a tutor or has a problem that needs to be addressed. Talk candidly with them if they call. If they haven't reached out to you but you've noticed any of the signs above, pick up the phone.
Your child might just be having a bad day. Look for patterns. If you're concerned, contact her teachers. Most importantly, talk to your child, and don't get frustrated if it takes her a while to open up.