Yes, modern screenwriting classes hammer home some variation of the five-act structure and, the particular beats to hit at each point. It's rare for any narrative film, even indies, to deviate from it much, and you are absolutely told to map out your whole narrative and know where it's going before you begin.

I'm sure there are some screenwriters who ignore all that and just start writing. Particularly if they're experienced enough to have an intuitive grasp of structure. But if you're a first time writer and reach the night before a submission deadline and you haven't even finished the first draft, then you've got serious problems. Leaving aside the ending, any script needs multiple revisions with time in between so that you come back it with clear sight.