Today at my school, I noticed on the back of my milk carton, it said Tetra something, and there was a triangle symbol. Not a tri-force, but a triangle with a circly design. So next time you buy one of those small milk cartons, check all over to see the Tetra symbol. I don't know if you get the same brand though.
By the way, I don't ...usually....read milk boxes....i was bored.