Hi Natalie,
I am currently studying the science section unfortunately there are some areas that wouldn't be suitable for a 9 year old and then there is other science content that your child can learn here is what I would recommend highly which is fun and interactive for your child at this age,

Computer programming is perfect as it falls under computer science your child can learn to make Webpages, games etc.
https://www.khanacademy.org/computing/computer-programming

Next thing you can explore is Pixar in box teaching mathematics, science , computer science and overall Animation you learn from the Pixar team with fun cute characters for your child's age would be perfect

https://www.khanacademy.org/partner-content/pixar

Next we have home made robots
https://www.khanacademy.org/science/electrical-engineering/robots

Nova labs was the most exciting and I am sure your child would love this a partnership with PBS you will find learning games as well

https://www.khanacademy.org/partner-content/nova

This may be a option as well with science projects that are very simple
https://www.khanacademy.org/science/physics/discoveries

These all include science but are really interactive for your child who is nine years old I hope these suggestions help as the Health and Medicine have been learned more at the youngest I know of is 13 and up and I don't know if your child is really at the age to comprehend physics,chemistry etc. I highly recommend the above they are simple ,fun and definitely informative your child will learn allot!