Some of the adults involved may not have much patience, know HOW to teach, or have knowledge of the subjects they should teach their child. Let's talk briefly here about competency in subjects. Consider there are all kinds of math tutor programs online, CD roms, and paid tutor services which you can use. You'll have to do your own research on tutors. There are also programs using cable television you can subscribe to and record.
Seasoned teacher instruct the classes, which are in classroom settings.
The point is, you live in an interactive world and have unlimited resources and options. Try to relax. Also, consider if a relative could teach the subject which you feel is your weak area. All of these interact in some manner with your children. You MUST also consider your child is a contributing factor in a school learning environment.