There are so, so many resources available to families right now, but they're also spread all over the internet! To help make things a little easier, here are some tried n true websites that I've grouped by general age and skill.
PreK - Upper Elementary
Reading: https://www.storylineonline.net/ -- Storytime for kids! Available via YouTube or other online players.
General Resource: https://lacountylibrary.org/ -- If you live in LA County, you can get a library card!
Science & Geography: https://www.nationalgeographic.org/education/classroom-resources/learn-at-home/ -- Beautiful resources for natural science and for exploring our world at large
Enrichment: https://www.si.edu/exhibitions/online -- I grew up in the Washington D.C. area and hold the Smithsonian in a special place. Now we can ALL experience the best of our national museums.
Math: http://bedtimemath.org/ -- Gameify math! Free app, no scores, no tests, just making math fun. I use this one with my students all the time to foster a healthy love of math. It's all around us and not scary!
Donald in Mathmagic Land https://www.youtube.com/watch?v=U_ZHsk0-eF0 -- Spark an interest in more than just flat numbers!
Math: https://www.khanacademy.org/math/k-8-grades -- find and drill problem areas in math.
Connections: https://teachrock.org/distancelearning/ -- this one is best used with a guide or a tutor, but if you have a self-starter it can be a GREAT resource to connect subjects and topics with music.
Social Studies / Current Events: https://newsela.com/ -- now more than ever it is important for our kids to learn to think critically about the world around them. This site curates news articles for students.
ACT/SAT Prep -- At the very least, buy the Official ACT Prep Guide (the Red Book) or the Official SAT Prep Guide. Those have the REAL tests. For these monster exams, I strongly recommend study sessions with a guide.
AP Classes -- I also recommend study sessions!
English: https://www.commonlit.org/ -- Common literature for high school aged students.
English: www.sparknotes.com -- I'm sure some teachers hate SparkNotes, but when used as a resource (not a primary source) it can help add a wonderful layer to a student's understanding of literature!
Writing: www.easybib.com -- Why on earth would you memorize citation styles anymore? Free that brain space.