A parent must know what level of math and any other subject, for that matter, that their child is performing at every school year. When children enter kindergarten and the school recommends that children know their ABC's and know how to count to twenty or whatever number, it is the parent's responsibility to make sure the child is prepared prior to enrolling in school.
Some of the software is developed in a game format. Children will think that they are playing a game, but in reality are actually learning math. Technology can be great, but I must warn parents to not allow children to spend a lot of unsupervised time on the computer.
Use things around the house that they already know and love! : My son has a HUGE adoration for his Thomas Trains... he can tell you every single trains name, number and color. When we started working on recognizing numbers and colors, I tried to use posters, games, workbooks, etc that would help him learn to recognize them... all to no avail! One day, we were playing with his trains, and HE asked me what number one of the trains was. Bells went off in my head and I realized that I could cater his natural curiosity about his beloved trains, and still be 'teaching' him to recognize numbers at the same time!
Elementary teachers and parents play the biggest role in a child's mathematical development, especially from Kindergarten through Fourth Grade. Time spent in school learning math or not learning math can never be replaced. Parents should make sure the elementary math teacher is knowledgeable and is a good teacher.