I am curious if anyone has some great (and preferably free) resources for kid lessons on all subjects.

My son is in kindergarten and while he has homework, I’d like to supplement every now and then depending on what they are studying in class. For example, this week they are leaning all about plants.

He really really enjoys looking at non-fiction books (especially about science) and is obsessed with workbooks.

My goal is not to overwhelm him with additional “work” but since he likes learning about things so much, I was hoping to find a place were I can find print outs, etc. Instead of hunting for a new book on every last subject (which is my instinct).