W tej szkole sekretariat jest na pierwszym piętrze, obok pokoju dyrektorki.

Because w meaning in or at takes the locative case when it refers to location.

So:

• basic form: ta szkoła = this school
• after w: w tej szkole = in this school

Both words change:

• ta → tej
• szkoła → szkole

This is a very common pattern in Polish.

It is the locative singular.

You use the locative after certain prepositions, especially ones connected with location, such as:

• w = in, at
• na = on, at
• o = about

So in this sentence:

• w tej szkole = in this school

The adjective/demonstrative and the noun both have to match in case, number, and gender.

Sekretariat usually means the school office, administrative office, or front office rather than a private secretary’s room.

In a school context, it is the place where administrative staff work, where you might ask for documents, information, or speak to office staff.

So it is often best understood as the school office.

Jest means is.

In Polish, the verb to be is sometimes omitted in sentences like To mój brat = This is my brother, but with location it is normally used.

So:

• Sekretariat jest na pierwszym piętrze = The office is on the first floor

Without jest, the sentence would sound incomplete or unnatural here.

In Polish, floors of a building are usually expressed with na.

So you say:

• na parterze = on the ground floor
• na pierwszym piętrze = on the first floor
• na drugim piętrze = on the second floor

Even though English often says on too, learners sometimes expect w because it also means in. But with floors, na is the normal Polish choice.

Because pierwszym piętrze is also in the locative singular after na.

The noun is:

• piętro = floor

After na for location, it becomes:

• na piętrze

The adjective has to agree with it:

• pierwsze piętro = first floor
• na pierwszym piętrze = on the first floor

So pierwszym is simply the locative form of pierwsze here.

Be careful: this can be confusing.

In Polish:

• parter = ground floor
• pierwsze piętro = the floor above the ground floor

So:

• in American English, pierwsze piętro usually matches first floor
• in British English, pierwsze piętro usually matches second floor

This is one of the most common sources of confusion for English speakers.

Because obok takes the genitive case.

So:

• basic form: pokój = room
• after obok: pokoju = of the room / next to the room

In this sentence:

• obok pokoju dyrektorki = next to the headmistress’s office / next to the principal’s room

Other prepositions that often take the genitive include bez, dla, od, do, and z in some meanings.

Because dyrektorka is in the genitive singular after obok pokoju.

The phrase is built like this:

• pokój dyrektorki = the headmistress’s room / the principal’s office

Here dyrektorki means of the female director/head teacher/principal.

So:

• dyrektorka = female director / female principal / headmistress
• dyrektorki = of the female director / principal

Yes. Dyrektorka is specifically feminine.

So:

• dyrektor = a male director, or sometimes a gender-neutral traditional form depending on context
• dyrektorka = a female director

In this sentence, the room belongs to a woman, so dyrektorki is used.

If it were a man, you would say:

• obok pokoju dyrektora

The comma separates an added location detail.

The main statement is:

• W tej szkole sekretariat jest na pierwszym piętrze = In this school, the office is on the first floor

Then obok pokoju dyrektorki adds extra information:

• next to the principal’s room

In everyday writing, this comma is natural because the second phrase works like an additional clarification of location.

Yes. Polish word order is fairly flexible, although different orders change the emphasis.

The original sentence:

• W tej szkole sekretariat jest na pierwszym piętrze, obok pokoju dyrektorki.

This starts with W tej szkole, which sets the scene: In this school...

Other possible versions include:

• Sekretariat jest w tej szkole na pierwszym piętrze, obok pokoju dyrektorki.
• Na pierwszym piętrze, obok pokoju dyrektorki, jest sekretariat.

These are possible, but the original sounds very natural and neutral.

Here is the full breakdown:

• W tej szkole

  • w
    • locative
  • tej szkole = locative singular

• sekretariat

  • nominative singular
  • it is the subject of the sentence

• jest

  • verb: is

• na pierwszym piętrze

  • na
    • locative
  • pierwszym piętrze = locative singular

• obok pokoju dyrektorki

  • obok
    • genitive
  • pokoju = genitive singular
  • dyrektorki = genitive singular

So this one sentence gives you a nice example of locative and genitive in natural use.

Yes, often you can.

Both obok and koło can mean next to or near.

• obok pokoju dyrektorki = next to the principal’s room
• koło pokoju dyrektorki = near / by the principal’s room

Obok often feels a bit more clearly like right next to, while koło can sometimes be slightly broader, like nearby, though in many contexts they overlap.

Yes. Literally, that is how it is built.

Polish often expresses possession with two nouns, where the second one goes into the genitive:

• pokój nauczyciela = the teacher’s room
• gabinet lekarza = the doctor’s office
• samochód brata = the brother’s car / my brother’s car

So:

• pokój dyrektorki literally = room of the female principal/director
• in natural English = the principal’s office or the headmistress’s room