Many kids simply have no idea. Taxes are a concept more for your children that have a good handle on some basic money concepts. Talk to them about the different types of taxes before they start into part time jobs or their own business.
Your Children may know about some coin terms like Medicaid and Social Security, but not have any idea what these taxes actually do. Explain the different types of taxes to your children and how they might encounter them in their life. From sales tax to income, show how each affects them.