I'd like to ask for advice. My students were supposed to use the present simple and the present progressive to express the future in a few sentences from a test. The task read "Emphasize that the action will definitely happen in the future" and the sentences were:
(1) The train ___ (arrive) at 6 p.m. tomorrow.
(2) Tom ___ (go) on* a business conference to Chicago next Wednesday.
(3) Mike invited us to his place. He ____ (have) a party tomorrow evening.
Some of them used the present simple in (1) and the present progressive in (2) and (3) (that's what the test compiler and the coursebook want them to use), but the majority went for the will-Future in all the three. I know the Future simple can be used to express the ideas based on timetables/schedules; besides, it can also be used to express absolute certainty. My students aren't aware of that; but even so, I'm not sure if I should mark their answers as 'wrong'. Would you?
* I guess we go to conferences, not on, don't we?