DAI RISPOSTE - English

Ummmm, no.

It depends on which question is being asked and the relevant importance of the timeframe verses the action performed.

For example, if you ask a question ”What will you do at (British) / on (American) the weekend”,. then, if the action of shopping is more important, then the questioner’s sentence form is perfectly correct.

If the time is the more important aspect of the communication, then ”tomorrow” goes at the beginning of the sentence. A comma is optional if it is British English (the presence or absence of the comma communicates other information - can you see why?).

Incidentally, your hypothetical ”English teacher” would be almost certainly a speaker of American English, only able to function using a formal register of American English and has learnt that rule by rote from a poorly formulated grammar book of American English. I’ve seen some real garbage out there with ”Grammar Book” written on the cover.

And yes, the writer of the aforementioned grammar text is almost certainly clueless about sentence order and meaning, and probably he/she only functions linguistically using a formal register. They have likely misunderstood that putting the timeframe at the start of a sentence is not a law with physical validity, but something which occurs in a majority of cases in formal writing because times in timetables/schedules are usually more important for people like managers than for what actually happens during that time.