This starts with meeting your child's teacher and seeing for yourself what goes on at school. I invite parents to visit my classes at any time. This often seems to amaze them. If you're at home, if you're not working, come sit in the back of my classroom. The school is open to you.
Parents can actually have a negative effect on math education, usually without realizing it.
I frequently find that students' negative attitudes about math stem directly from parental comments. The irony is, even adults who 'hate' math are probably using it much more than they think. This often has quite an effect on parents, who realize that, in fact, they use math quite a lot. Mathematics is a subject in which we have to create thinkers, not memorizers. If students are to become the thinkers of tomorrow, we can't just concentrate on getting them to pass tests.