Kids Keep Bringing in Acorns

As the title states, my students keep bringing in acorns. They actively look for them during recess and pocket them.

We'll be sitting in class and I hear something hit the floor. Surprise, it's the acorns! On rare occasions, it'll be rocks.

I go out with them during recess once the acorn-pocketing begins and we leave them outside or plant them with permission.

I'm not really sure how they keep finding the acorns though. There's no trees on or near school grounds. And I know they aren't bringing them from home.

Edit: I have no intentions of banning the acorns because I did the exact same thing at their age and know exactly how that's going to play out.

I think I'm going to get a 5gal bucket from the high school ag teacher and put the acorns in it to get things a little more under control.

And thank you for all the possible lesson plan reccomendations.