Here is a sentence from a textbook. The task is to choose the correct tense, Past Simple or Present Simple:
When your lessons (to be) over on Monday?
To me, both can be used here, as the context is very small. Is it right?
Since on Monday can refer to next Monday, or to a Monday in the recent past, this past Monday, or even to Mondays in general (a native speaker might not say "on Mondays" but on Monday to refer to a day of the week in general terms when asking about a recurring schedule) future, past, and present tenses are all valid here. But the location of the verb must shift.
When will your lessons be over on Monday? (Monday next, or Mondays in general*)
When were your lessons over on Monday? (probably the most recent Monday, this past Monday; a specific Monday in the distant past would be "that Monday" -- the police might ask "And where were you on that Monday?" to refer back to a particular Monday which is germane to their line of questioning)
When are your lessons over on Monday? (Mondays in general*, or Monday next)
*some might consider this slightly below the standard "Mondays"