Visit your state's department of education website. Look for parent and teacher resources that discuss state standards for curriculum and student knowledge. These pages often include links to state and national resources, lesson plans, worksheets and education websites. These resources are often free for anyone to use.
Visit the websites for public schools in your area that correspond to the ages of your children. Teachers often posts syllabi, samples of student work, assignment lists and even lesson plans. Visit more than one school website and do some exploring to find everything you can.
Look for spelling lists, reading lists and study guides for your student's grade level. Print them out or bookmark them to use later. Check for grading rubrics that you can use or tweak for your own students. These are especially helpful for teaching and grading writing skills.
Read class descriptions to make sure you are covering similar topics and subjects. Check out the graduation requirements to help you stay on track with your teen students.