Write down how you feel about math. Are you afraid of it? Do you avoid math problems whenever you can? You may be transferring your aversion to math to your child.
Sit down with your child and do some simple problems. See how he reacts. If your child has severe math anxiety, he will become frustrated and agitated. Increase the difficulty of the problems to test the child's knowledge, and include algebra, fractions, and quadratics if he is of the appropriate age.
Talk to your child's teachers about how she is doing in math. Discuss whether your child actively takes part in the class or listlessly slumps at the back, visibly bored. Discuss grades, as poorer grades indicate difficulty with math, which may lead to frustration and anxiety.
Print out and ask older children to take the anxiety test at mathpower. This gives you an idea about the strength of their feelings about math.
If either you or your children do suffer from math anxiety, reassurance is the key to reducing it. Restart with the basics. Have fun sessions involving pizzas and other treats to teach fractions; when walking, ask them how much of the sky is covered with clouds to get them used to percentages, and ask other innocent questions. Remind them about their successes, and reinforce the message that they can do math.