Learn Hardcore Croatian: Učionica je bila bučna, pa je učiteljica morala isključiti glazbu na računalu. - The classroom was noisy, so the teacher had to turn off the music on the computer.

Učionica je bila bučna. – The classroom (fem.) was noisy.
Razred je bio bučan. – The class (masc.) was noisy.
Djeca su bila bučna. – The children (neuter plural form of participle) were noisy.

So we use bila because učionica is grammatically feminine.

What is the difference between učionica and učiteljica?

učionica – classroom (the room itself)
- noun, feminine, singular: učionica
učiteljica – female teacher
- noun, feminine, singular: učiteljica

The masculine form učitelj means male teacher.

So in the sentence:

Učionica je bila bučna – The classroom was noisy
učiteljica je morala… – the (female) teacher had to…

Why is it učiteljica je morala, not učiteljica je morao?

Again, agreement with gender:

morala – past participle of morati (to have to), feminine singular
morao – masculine singular

Since učiteljica is feminine:

Učiteljica je morala isključiti glazbu. – The (female) teacher had to turn off the music.

If it were a male teacher (učitelj):

Učitelj je morao isključiti glazbu.

What is the function of pa here? Does it mean and, so, or but?

In this sentence, pa roughly means so or and so:

Učionica je bila bučna, pa je učiteljica morala isključiti glazbu…
= The classroom was noisy, so the teacher had to turn off the music…

Pa is a very common connector. Depending on context, it can feel like:

and / and then
so
sometimes a mild but / yet

Here it shows a causal consequence, similar to so.

You could also use:

…bila bučna, zato je učiteljica morala… – …was noisy, therefore the teacher had to…
…bila bučna, jer je učiteljica morala… would be wrong here, because jer means because and would reverse the logic.

What exactly does morala isključiti mean? Is this like had to turn off?

Yes:

morala – had to (feminine past of morati – to have to, must)
isključiti – to switch off / to turn off (perfective verb)

So morala isključiti = had to turn off.

The structure is:

morati
- infinitive (any verb)
  - moram isključiti – I have to turn off
  - morala je isključiti – she had to turn off

Why is it isključiti glazbu, and what case is glazbu?

Isključiti is a transitive verb (it takes a direct object), so its object is in the accusative case.

glazba – nominative (dictionary form)
glazbu – accusative singular (direct object)

So:

isključiti glazbu – to turn off the music

Other examples:

čuti glazbu – to hear music (accusative)
slušati glazbu – to listen to music (accusative)

What’s the difference between glazba and muzika?

Both mean music, but there is a nuance in usage:

glazba – the more standard Croatian word; preferred in formal contexts, education, media in Croatia.
muzika – also widely understood and used, but often felt as more colloquial or influenced by other regional standards (Serbian, Bosnian, etc.).

In a Croatian school sentence, glazba is the natural choice:

isključiti glazbu – turn off the music

Why is it na računalu and not na računalo?

Here na računalu uses na + locative to express location:

računalo – computer, neuter noun
na računalu – on the computer (locative case, static location)

Basic pattern:

na + locative – where something is (location)
- na stolu – on the table
- na računalu – on the computer (on the device)

Na računalo (accusative) would be used for movement onto the computer (which usually doesn’t make sense literally, except in very specific contexts). Here we mean the music that is playing on the computer, so locative računalu is correct.

Could you say isključiti glazbu s računala instead of na računalu?

Yes, but the meaning shifts slightly:

isključiti glazbu na računalu – turn off the music on the computer (music playing from that computer)
isključiti glazbu s računala – more like remove / disconnect music from the computer, or stop music coming from the computer; it sounds less standard for this simple “turn off” meaning.

In everyday speech about stopping playback, na računalu is more natural.
S računala is more often used when transferring or removing files:

Kopirati datoteke s računala. – Copy files from the computer.

Why is bučna used, and what’s the difference between bučan and glasno?

bučan / bučna / bučno – noisy, an adjective describing something or someone.
glasno – loudly, an adverb describing how something is done.

In our sentence:

učionica je bila bučna – the classroom was noisy (adjective, feminine singular: bučna)

If you want to say they were talking loudly, you’d use glasno:

Učenici su glasno pričali. – The students were talking loudly.

So:

bučna učionica – a noisy classroom
pričati glasno – to speak loudly

Why does bučna end in -a?

Adjectives in Croatian agree with the noun in:

gender
number
case

Učionica is:

feminine
singular
nominative (subject of the sentence)

So bučan (noisy) must be:

feminine singular nominative: bučna

Patterns for bučan (singular, nominative):

masculine: bučan – bučan razred (a noisy class)
feminine: bučna – bučna učionica (a noisy classroom)
neuter: bučno – bučno dijete (a noisy child)

Is it normal to have je twice in one sentence: je bila and je morala?

Yes, that’s completely normal.

Each je belongs to its own verb phrase:

učionica je bila bučna – the classroom was noisy
(učiteljica) je morala isključiti – the teacher had to turn off

Each clause has its own auxiliary:

First clause: je bila
Second clause: je morala

Joined by pa, they form one complex sentence, but grammatically they are two clauses, each with its own je.

Could I change the word order, for example: Učiteljica je morala isključiti glazbu na računalu jer je učionica bila bučna?

Yes, that’s a very natural alternative:

Učiteljica je morala isključiti glazbu na računalu jer je učionica bila bučna.
– The teacher had to turn off the music on the computer because the classroom was noisy.

Differences:

Original: cause first, then consequence
- Učionica je bila bučna, pa je učiteljica morala… – The classroom was noisy, so the teacher had to…
Alternative: consequence first, then reason
- Učiteljica je morala… jer je učionica bila bučna. – The teacher had to… because the classroom was noisy.

Both are correct; you just change which part you emphasize.

What is the difference between učionica and razred?

Both relate to school, but they are not the same:

učionica – classroom (the physical room)
razred –
- class as a group of students (e.g. 5th grade, 8B)
- also grade/year level

Examples:

Učionica je bila bučna. – The classroom was noisy.
Cijeli razred je bio bučan. – The whole class (group of students) was noisy.
On ide u peti razred. – He is in the fifth grade.