Learn Hardcore German: Nach der Pause gehen die Schülerinnen ruhig in die Klasse zurück. - After the break the female pupils go back to the classroom calmly.

With places (mostly countries/cities):
- nach Berlin, nach Deutschland → to Berlin, to Germany
With time expressions or events (like here):
- nach der Pause → after the break
- nach dem Unterricht → after class
- nach dem Essen → after eating / after the meal

In your sentence, nach der Pause clearly refers to time, so it means after the break, not to the break.

Why is the verb gehen in second position after Nach der Pause and not after the subject?

German main clauses follow the verb-second (V2) rule:

The conjugated verb must be in position 2 of the sentence.
Position 1 can be almost anything (subject, time, place, object, etc.).

In your sentence:

Nach der Pause = position 1 (a time phrase is put first for emphasis)
gehen = position 2 (conjugated verb)
die Schülerinnen ruhig in die Klasse zurück = rest of the sentence

If you start with the subject instead, the verb still stays second:

Die Schülerinnen gehen nach der Pause ruhig in die Klasse zurück.

Both orders are correct; they just emphasize different parts.

What exactly does die Schülerinnen mean, and how is it different from die Schüler?

der Schüler = male pupil (singular)
die Schülerin = female pupil (singular)
die Schüler = male pupils (plural), or traditionally mixed group (generic masculine)
die Schülerinnen = female pupils (plural) only

So die Schülerinnen refers specifically to a group of girls.

In modern German, people increasingly avoid using die Schüler as a generic for mixed groups and instead use forms like:

die Schülerinnen und Schüler – “female and male pupils”
or gender-neutral alternatives, depending on context.

Why is Schülerinnen and Klasse capitalized, but ruhig is not?

In German:

All nouns are capitalized:
- die Schülerinnen, die Pause, die Klasse
Adjectives and adverbs are not (except at the beginning of a sentence or in titles):
- ruhig

So capitalization tells you that Schülerinnen, Pause, Klasse are nouns, while ruhig is an adjective used adverbially here.

Why does ruhig have no ending (like ruhige) in gehen die Schülerinnen ruhig?

Here ruhig is an adverb describing how they go (they go calmly/quietly).

In German:

As an adjective before a noun, it takes an ending:
- die ruhige Klasse – the quiet class
As a predicate adjective after “sein/werden/bleiben”, it has no ending:
- Die Klasse ist ruhig. – The class is quiet.
As an adverb (describing a verb), it also has no ending:
- Die Schülerinnen gehen ruhig. – The pupils walk quietly.

In your sentence, gehen is the verb, so ruhig is an adverb → no ending.

Why is it in die Klasse and not in der Klasse?

The preposition in is a two-way preposition. It can take:

Accusative when there is movement into a place (direction):
- in die Klasse – into the class / classroom
- in den Park gehen – go into the park
Dative when it describes location (no movement):
- in der Klasse – in the class / classroom
- im Park sein (= in dem Park) – be in the park

Your sentence shows movement into the classroom, so in takes the accusative: in die Klasse.

Does Klasse mean “class” (the group of pupils) or “classroom” (the room)?

Klasse can mean both, depending on context:

The group of pupils:
- Meine Klasse ist laut. – My class is loud.
The room (especially at school, in everyday speech):
- Wir gehen in die Klasse. – We go into the classroom.

In your sentence, in die Klasse naturally means into the classroom, because they are physically going somewhere. For extra clarity, German can also say:

ins Klassenzimmer gehen – go into the classroom

but in die Klasse is very common in school contexts.

What is the role of zurück at the end? Is zurückgehen one verb?

Yes, zurückgehen is a separable verb (prefix verb):

zurück = back
gehen = to go
zurückgehen = to go back

In main clauses, separable verbs split:

Sie gehen zurück. – They go back.

When you add more material, the prefix stays at the end of the sentence bracket:

Nach der Pause gehen die Schülerinnen ruhig in die Klasse zurück.

Here gehen … zurück belongs together as the verb, and in die Klasse is the destination of this “going back”.

You could also say:

Nach der Pause gehen die Schülerinnen ruhig zurück in die Klasse.

The meaning is the same; the difference is just word order and emphasis.

Could I also say Nach der Pause kommen die Schülerinnen ruhig in die Klasse zurück?

You can say that, but the nuance changes:

gehen focuses on the movement from the pupils’ point of view (they are walking back).
kommen focuses on arrival from the speaker’s point of view (they are coming back to where the speaker is).

Typical use:

A teacher waiting in the classroom would more naturally say:
- Nach der Pause kommen die Schülerinnen ruhig in die Klasse zurück.
A person walking with the pupils away from the playground might say:
- Nach der Pause gehen die Schülerinnen ruhig in die Klasse zurück.

Both are grammatical; the choice depends on perspective.

The English translation might use “will go back” or “go back” regularly. Why is German just using gehen in the present tense?

German Präsens (present tense) is used more broadly than English present simple. It can express:

A regular habit:
- Nach der Pause gehen die Schülerinnen ruhig in die Klasse zurück.
  → After the break, the pupils (always) go back quietly into the classroom.
A future event, when time is clear from context:
- Morgen gehen wir in die Stadt. – Tomorrow we’ll go to town.

So your sentence in German present tense can be translated as:

After the break, the pupils go back quietly to the classroom. (habit)
or
After the break, the pupils will go back quietly to the classroom. (one future event)

No werden (future form) is needed in German unless you really want to emphasize the futurity.