I teach the upper grades in my school, yet I continue to see kids who do not even have basic algebra skills in place. As a parent, I'm very aware of what my own children are learning in school. For the most part, I've been happy with their progress, but as they rise in grade level, I'm starting to see more emphasis on a loose understanding of the concepts and less emphasis on skills__particularly skills with arithmetic of fractions. The main problem with what I see with my students and my own children is that kids are taught "concepts" and are not taught skills__unless they're lucky enough to have a teacher who knows better. Most particularly, children are not taught mastery of arithmetic with fractions. Unfortunately, virtually all of their future math education depends on being able to do fractional arithmetic.
There are many math_based games available in educational toy stores that will help to reinforce the principles your child learns in worksheets. Computer games can help too, but depending on the age of your child, it is best not to encourage too much computer use at an early age. Everyday activities can be turned into math lessons too. A trip to the grocery store can turn into a math lesson if you encourage your child to help you count how many items you are buying, or add up the bottles of milk as you add them to your cart.