You can search a skill your child is working on in Math class, i.e. Multiplication with the Area Model, and it will show you a video of a teacher teaching that skill. Most lessons also have an online practice for the skill as well. 

I.W. Evans utilizes a math program called IXL. This program will identify gaps in learning and provide practice. There are tutorial videos and examples to help students. 

Learning Farm provides an online lesson and games to practice skills, and a test over the skills.