When I arrived home, Mom was still in/at her yoga class.
Should one use in or at in this situation. And why?
When I arrived home, Mom was still in/at her yoga class.
Should one use in or at in this situation. And why?
Assuming that the yoga class is taking place elsewhere, at would be usual. (She is at the place where the class is held, not at home.)
If the speaker was in the same building, perhaps having just attended a different class, they might say 'Mom is still in her yoga class'.
I hate to disagree with Kate Bunting, but, at least in spoken American English, both "in" and "at" are acceptable. She is both where the class takes place ("at"), and she is a part of the class ("in").
According to Ngram, "in class" is far more common in written American English, but I do not rely too heavily on Ngram. First, it cannot cope with speech, and my impression is that "at class" is quite common in American speech. Second, Ngram is independent of context, and context may influence the choice of preposition.