Music is, effectively, a sequence of sound frequencies. An especially pleasing sequence to hear (okay... depending on the music) but a sequence of them nonetheless. This already sounds like it has enormous potential for cross-curricular overlap with math and/or science. Measurement of the "second difference" between different frequencies, perhaps? Comparison of how "loud" different frequencies at the same number of decibels feel? Likewise, physical education is all about motion. Motion among students, and in the context of sports, motion among the volleyballs, basketballs, etc... that they are tossing around. This too sounds like it has enormous potential for cross-curricular overlap with math and/or science. Graphing of one's own motion as one does laps around the gym, perhaps? Physics problems analyzing future and/or past sports plays? Theatre and art, of course, can be used to represent a wide variety of topics. I had a history teacher who had individual students volunteer to represent the role of whole countries in an introductory skit for the World War 1 unit. Can similar cross-curricular projects be done to represent the roles of different chemicals in photosynthesis? To represent the orbits of different planets? I've taught at schools that had poster projects for math units, which feels a little unfair to students who aren't as good at drawing. What arrangement could be made for cross-curricular content that's a little more fair to those who chose art of their own accord? What ideas have the rest of you come up with for cross-curricular content? I find the only stuff I managed to come up with over my teaching career was stuff that was either between core courses and other core courses, or, if involving a special subject (media tech) then literally only cross-curricular in the sense of "do a video project, involving material from any of your other courses, on [insert theme here]." There wasn't anything tying it to a specific other subject.