Learning begins in the home -- whether parents realize it or not, students are like sponges. In the first few years of life, children learn an astounding number of tasks, from crawling and walking to intelligible speech and fine motor skills, and parents are the closest sources that help guide young individuals through these new and uncharted waters. Children pick up on and emulate the attitudes that are presented day in and day out in the home, so making sure to emphasize the value of education as a family is extremely important.
Children, especially young ones, are malleable and do not always know how to compartmentalize (which parents can use to their advantage). What goes on in the home will impact the classroom, and vice versa. For this reason, parents should take care to remain positive about education, regardless of their personal experiences with it. If you were "bad at mathematics" when you were in school and frequently mention this in front of your child, you will soon find them stating that they're "bad at mathematics" as well -- and that they cease trying, instead attributing low grades to being inherently poor in the subject. With no real reason for that decision other than opinion, as it is not based on the level of difficulty or passion for the subject, you have now effectively convinced your child that he or she will not like mathematics or cannot be good at it since you weren't. Use the fact that your children are impressionable to make English readings and History lessons entertaining. If you act like you are enjoying it, they will, too.
There are many methods to demonstrate to your children that you care about their education and to help ensure that they also value it even after they leave the house. Work on assignments with them and discuss accordingly; make sure you ask about what they are learning and what they have coming up in the way of tests. Even just sitting with your student while they do their homework in the evening proves that you care that they are prepared for their "jobs" as learners. It also allows them easy access to you when they have questions about how to approach a problem.
Valuing education for the sake of expanding your children's worldviews and preparing them for college is wonderful, but there are multiple other fringe benefits too! Several studies link valuing education (and being successful academically) with improved health, increased cognitive development, decreased risk of depression and other mental illnesses, increased ability to appropriately cope with stress and anger, better decision-making skills, and overall increased quality of life. These bonuses are positive -- why not stress education's importance with your children?
Parents who assume an active role in their students' education will be directly able to teach them the worth of academic aptitude. Education is something that can never be taken from you, so it is a wonderful, lasting gift that you can and absolutely should give to your children.