Nasza klasa jest na drugim piętrze.

It can mean either, depending on context.

In this sentence, because we are talking about a location — na drugim piętrze — English will often translate it as our classroom is on the second floor.

But klasa in Polish can also mean:

• a class of students
• a school year / form
• a classroom, in some contexts

If you want to be completely unambiguous, sala or sala lekcyjna is often clearer for classroom.

Because nasza has to agree with klasa.

Klasa is:

• singular
• feminine

So the possessive adjective our must also be:

• singular
• feminine

That gives nasza.

Compare:

• nasz dom = our house (dom is masculine)
• nasza klasa = our class/classroom (klasa is feminine)
• nasze okno = our window (okno is neuter)

In a normal full sentence like this, jest is standard and expected.

Nasza klasa jest na drugim piętrze = Our classroom is on the second floor.

If you remove jest:

• Nasza klasa na drugim piętrze

it sounds incomplete in standard Polish, unless it is a headline, note, label, or very informal shorthand.

So for learners, the safe rule is:

• use jest in ordinary sentences of this type

Because Polish normally uses na with floors of a building.

You say:

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

Using w here would sound unnatural or simply wrong in standard usage.

So this is something to learn as a fixed pattern:

• być na + floor

It is the locative case.

After na, when it means location and not movement, Polish uses the locative:

• na drugim piętrze = on the second floor

The basic form is:

• drugie piętro = second floor

But after na for location, it changes to:

• na drugim piętrze

So:

• drugie → drugim
• piętro → piętrze

Because adjectives in Polish must agree with the noun in:

• gender
• number
• case

The noun piętro is:

• singular
• neuter

And after na in a location phrase, it is in the locative.

So the adjective drugi also has to be:

• singular
• neuter
• locative

That gives drugim.

So the pair is:

• drugie piętro = nominative/accusative form
• na drugim piętrze = locative form

This is a very important Polish pattern:

• na drugim piętrze = on the second floor
  → location, where something is

• na drugie piętro = to the second floor
  → movement, where someone is going

Examples:

• Nasza klasa jest na drugim piętrze. = Our classroom is on the second floor.
• Idziemy na drugie piętro. = We are going to the second floor.

So:

• location → na + locative
• movement/destination → na + accusative

Not always, because floor numbering differs between languages and countries.

In Polish:

• parter = ground floor
• pierwsze piętro = the floor above the ground floor
• drugie piętro = the next one above that

So drugie piętro is:

• British English: usually second floor
• American English: often third floor

This is a very common source of confusion for English speakers.

Yes. Polish word order is flexible, though the basic version here is the most neutral:

• Nasza klasa jest na drugim piętrze.

You can also say:

• Na drugim piętrze jest nasza klasa.

That version puts more focus on the location: On the second floor is our classroom.

So Polish word order can change for emphasis, but it is not random. The neutral, safest version for learners is the original one.

A rough English-friendly approximation is PYEN-tshe.

A few helpful points:

• pię- sounds roughly like pyen
• trz does not sound like separate t-r-z
• the ending -rze / -trze has a sound that English does not match perfectly

Also:

• nasza ≈ NASH-a
• klasa ≈ KLA-sa
• jest ≈ yest
• drugim ≈ DROO-gim

The real Polish pronunciation is more precise than these spellings, but these approximations are a useful start.

Yes, it is a normal, natural sentence.

It sounds neutral and correct in everyday speech:

• Nasza klasa jest na drugim piętrze.

The only small nuance is that some speakers might prefer sala if they specifically mean the physical classroom:

• Nasza sala jest na drugim piętrze.

But the original sentence is still perfectly understandable and natural.