Here is a Cultural Literacy worksheet on the idiom high horse, as in “to be on one’s high horse.” This is still, I think, a relatively common expression in American English. In any event, it is one of those idioms that requires prior knowledge and interpretive skills–you know, those things that combine into semantic webs that we no longer teach for, preferring the narrow, blinkered tests that crappy educational publishers produce.
This is a half-page worksheet with a reading of one long, kind of complicated compound sentence; you may want to overhaul the text for emergent readers or students for whom English is a second or third language.
If you find typos in this document, I would appreciate a notification. And, as always, if you find this material useful in your practice, I would be grateful to hear what you think of it. I seek your peer review.