I’m really confused on which form to use. I’ve seen “in die Schule”, “in der Schule”, and “zur Schule” many times, yet I don’t know which and when I should use one. Could someone please explain this to me?
For example, I don’t know which of these sentences are correct:
In der Schule is the answer to the question where you actually are.
Wo bist Du gerade? In der Schule.
In die Schule is the answer to the question where you are headed.
Wohin gehst Du jetzt? In die Schule.
Please note that this mostly implies that you are also actually either enrolled there or work there.
Zur Schule is a bit ambiguous. It can either also answer the question where someone is currently headed.
Wohin gehst Du jetzt? Zur Schule.
Please note that this does not necessarily mean your are a student/teacher/otherwise employed there. It can mean that you are generally headed to the school as a meeting point.
But it can also be the general answer about your current "employment status".
Was machst Du? Arbeitest Du? Nein, ich gehe noch zur Schule.
As for the others:
Ich gehe in die Schule
Is correct. It means that you're on your way to school and class.
Ich gehe in der Schule
Is not as typical as the other sentences. It means that you are walking inside the school building (as opposed to running). It may also be a valid answer:
Musst Du noch auf's Klo? Nein, ich gehe in der Schule (aufs Klo)
That's actually a common use.
Ich gehe zur Schule
Correct, explained above.
Ich bin in die Schule
Almost never correct. Could be a very colloquial answer to a question, like
Was hast Du nach dem Frühstück gemacht? Ich bin in die Schule (gegangen).
Usually you'd expect a verb.
Ich bin in der Schule
Correct, see above.
Ich bin zur Schule
Like Ich bin in die Schule, used in the same contexts, but not correct when used by itself.
You would write "in der Schule" (dative) if you are talking about someone who is in the school.
Ich bin in der Schule.
You would write "in die Schule" (accusative) if you are talking about going to school.
Ich gehe in die Schule.
"Zur Schule" is equivalent to "in die Schule".
For example, I don't know which of these sentences are correct:
Under certain conditions all of them could be seen as correct - but watch the context ;-)
Ich gehe in die Schule.
Ich gehe zur Schule.
Ich bin in der Schule.
See explanation from @Tom Au
Some comments on the other sentences, which you may hear or read colloquially:
Ich gehe in der Schule.
means that you do something "to go to" not now, but later in school:
"Warst du schon auf der Toilette?" - "Nein. Ich gehe in der Schule (auf die Toilette)".
The sentence
Ich bin in die Schule.
is actually wrong. You could say "Ich bin in die Schule gegangen" (perfect tense).
However, mostly less educated people, or people talking dialect, sometimes don't decline at all. They use the basic form ("die Schule") in all cases. Only in this context, the sentence is equivalent to "Ich bin in der Schule". You should use it neither in writing nor speaking.
Another possible construction is:
"Ich habe dich gestern auf der Straße gesehen. Wo bist du hin(gegangen)?" - "Ich bin in die Schule (gegangen)"
The same applies for
Ich bin zur Schule (gegangen).
