Razrednica je u dnevnik stavila napomenu da svi donesu bilježnice.

Razrednica is a feminine noun meaning the female class teacher / homeroom teacher / form teacher.

It comes from:

• razrednik = a male class teacher
• razrednica = a female class teacher

So the sentence specifically refers to a woman. That is also why the verb later appears in the feminine form stavila.

Je stavila is the normal Croatian past tense form.

Croatian past tense is usually made with:

• the auxiliary biti in the present tense
• plus the l-participle

Here:

• je = has / is as an auxiliary
• stavila = past participle, feminine singular of staviti

Together, je stavila means put / placed / wrote down in the past.

Croatian often puts the auxiliary in the second position in the clause, so:

• Razrednica je stavila ...

That word order is very standard.

Because the subject razrednica is feminine singular.

In the Croatian past tense, the participle agrees with the subject in gender and number:

• masculine singular: stavio
• feminine singular: stavila
• neuter singular: stavilo
• plural masculine/mixed: stavili
• plural feminine: stavile

Since razrednica is feminine, the correct form is stavila.

Because u can take different cases depending on the meaning.

Here the sentence expresses movement into something:

• she put a note into the register / diary

With motion toward the inside of something, Croatian uses:

• u + accusative

So:

• dnevnik here is accusative singular

Compare:

• u dnevnik = into the register
• u dnevniku = in the register

So the contrast is:

• stavila u dnevnik = she put it into the register
• piše u dnevniku = it is written in the register

In this sentence, dnevnik is most naturally a class register, school record book, or possibly a school diary/log.

Although dnevnik can also mean diary or journal in other contexts, in a school sentence with razrednica and napomena, it usually refers to an official school record.

So this is not necessarily a private diary. It is more likely an administrative school book or record.

Because napomenu is the accusative singular, used for the direct object of the verb staviti.

The basic form is:

• napomena = note, remark, comment

But after stavila (put), we need the thing being put, so we use accusative:

• stavila napomenu = put a note / entered a note

So:

• nominative: napomena
• accusative: napomenu

This is a very common -a noun pattern in Croatian:

• žena → ženu
• knjiga → knjigu
• napomena → napomenu

Here da introduces a subordinate clause meaning something like:

• that
• so that
• for everyone to

In this sentence:

• napomenu da svi donesu bilježnice

This means the note said or indicated that everyone should bring their notebooks.

Croatian often uses da + verb where English might use:

• that ...
• to ...
• should ...

So this structure is very common and important.

Donesu is from the verb donijeti / doneti, which is perfective and means to bring as a completed action.

Here, after da, Croatian often uses the present tense of a perfective verb to express something like:

• should bring
• are to bring
• bring (on that occasion)

So:

• da svi donesu bilježnice = that everyone bring / should bring notebooks

By contrast:

• donose is from donositi, the imperfective verb, meaning repeated or ongoing bringing

Very roughly:

• donesu = bring them, successfully, once, as a completed act
• donose = are bringing / bring regularly / keep bringing

In this sentence, the teacher wants a specific completed action, so donesu is the natural choice.

Here bilježnice is accusative plural.

The singular is:

• bilježnica = notebook, exercise book

Plural nominative:

• bilježnice = notebooks

For many feminine nouns, the accusative plural has the same form as the nominative plural, so here:

• bilježnice can mean notebooks as the object

In this sentence, it is the object of donesu, so it is accusative plural:

• donesu bilježnice = bring notebooks

Because svi is the form used for everyone / all (people).

Here it refers to students, so it is masculine plural in the mixed/human sense:

• svi = everyone, all of them

Even if the group includes girls, Croatian normally uses svi for a mixed group or for people in general.

Compare:

• svi učenici = all students
• sve bilježnice = all notebooks

So:

• svi = people
• sve = things, or feminine plural in some contexts

Croatian often leaves that idea unstated when it is obvious from context.

So:

• da svi donesu bilježnice naturally means
• that everyone should bring their notebooks

You could add a possessive if needed:

• svoje bilježnice = their own notebooks

So a fuller version could be:

• da svi donesu svoje bilježnice

But in many everyday situations, Croatian omits svoje because it is already clear that each student should bring their own notebook(s).

The sentence as given is very natural:

• Razrednica je u dnevnik stavila napomenu da svi donesu bilježnice.

But Croatian word order is fairly flexible, especially for emphasis.

Possible variations include:

• Razrednica je stavila napomenu u dnevnik da svi donesu bilježnice.
• U dnevnik je razrednica stavila napomenu da svi donesu bilježnice.

These can all be grammatical, but the original sounds neutral and natural.

One thing that tends to stay stable is the auxiliary in second position:

• Razrednica je ...
• U dnevnik je ...

That is a common Croatian pattern.

Probably not.

Because of the school context:

• razrednica
• dnevnik
• napomena

the most natural meaning is that she entered/wrote a note in the class register.

So although staviti literally means put, Croatian often uses it in a broader sense like:

• put in writing
• enter
• record
• add

In context, it is best understood as an administrative school note, not a physical slip of paper.

It is not a direct command in the form of an imperative, but it expresses an instruction or requirement.

So it is more like:

• that everyone should bring notebooks
• for everyone to bring notebooks

A direct imperative would sound different, for example:

• Neka svi donesu bilježnice. = Let everyone bring notebooks / Everyone should bring notebooks.

In your sentence, the command is reported indirectly through the note.

Stavila comes from staviti, which is a perfective verb.

Its imperfective partner is usually:

• stavljati = to be putting, to put repeatedly
• staviti = to put, to place, as a completed act

That matters because Croatian often distinguishes:

• ongoing / repeated action with imperfective
• completed single action with perfective

Here the teacher made one completed entry in the register, so stavila is exactly what you would expect.

A very literal breakdown would be:

• Razrednica = the female class teacher
• je stavila = put / has put
• u dnevnik = into the register
• napomenu = a note
• da svi donesu bilježnice = that everyone bring notebooks

So a literal rendering would be something like:

The class teacher put into the register a note that everyone bring notebooks.

That is not the most natural English, but it helps show the Croatian structure.