The University of Colorado at Boulder created a site full of dozens of interactive simulations in subjects such as physics, biology, chemistry, earth science, and math.
You can use this site alongside your lesson plans, of course, but it’s also a site where you could let the kids – especially young teens – freely roam, to pursue what interests them most.
The simulations are open source, meaning, new simulations are always being added, but it also means that your student could work on, and add, their own simulation to the site for others to use for learning! Each simulation goes through testing for accuracy.
How to Get This Freebie: Click the orange “Play with Sims” button.
Good Starting Points:
Access the Simulations by Grade Level
This Teacher Page has activities created by other educators
Recommended Grade Levels: All, from Elementary, to Middle, High and even College Level