Moja sestra vodi djecu u školu.

Because moja has to agree with sestra.

In Croatian, possessives like moj (my) change form to match the noun’s:

• gender
• number
• case

Since sestra is feminine singular nominative, the correct form is moja.

Compare:

• moj brat = my brother
• moja sestra = my sister
• moje dijete = my child

Sestra is in the nominative singular.

That is the case used for the subject of the sentence — the person doing the action. Here, moja sestra is the subject, because she is the one who vodi.

Vodi is the 3rd person singular present tense of the verb voditi.

So:

• ja vodim = I lead / take
• ti vodiš = you lead / take
• on/ona vodi = he/she leads / takes

Because the subject is moja sestra (she), the verb form is vodi.

The basic idea of voditi is to lead, to guide, or to take someone somewhere.

In this sentence, it is naturally understood as takes or is taking. With people as the object and a destination after it, voditi often means something like:

• escort
• lead
• take

So it is not just abstract lead here; it is a very normal way to say someone is taking children somewhere.

Yes.

Croatian present tense often covers both meanings that English splits into:

• takes
• is taking

The exact meaning depends on context.

For example:

• Moja sestra vodi djecu u školu svaki dan. = My sister takes the children to school every day.
• Gledaj, moja sestra vodi djecu u školu. = Look, my sister is taking the children to school.

So vodi can be habitual or happening now.

Because djecu is the accusative form, and the direct object of the verb must be in the accusative.

Here, the children are the ones being taken, so they are the direct object.

• dictionary form: djeca = children
• accusative form: djecu

So:

• Djeca dolaze. = The children are coming.
• Vidim djecu. = I see the children.

It means children, so in meaning it is plural.

However, djeca is a special Croatian noun with an irregular pattern, so its forms do not behave like a simple regular plural noun. That is why learners often notice forms like djecu and wonder where they come from.

A useful mini-pattern to remember is:

• djeca = children
• djece
• djeci
• djecu
• djecom

You do not need to force it into an English-style pattern; it is best learned as a common irregular noun.

Because this sentence expresses movement toward a destination.

With u:

• u + accusative = into / to
• u + locative = in / at

So:

• u školu = to school
• u školi = in/at school

That is why:

• Moja sestra vodi djecu u školu. = movement toward school
• Djeca su u školi. = location at school

Školu is the accusative singular of škola.

It is accusative because after u, when there is motion toward a place, Croatian uses the accusative.

Compare:

• škola = nominative
• školu = accusative
• školi = locative/dative

So u školu is literally the to school / into school form.

Because Croatian does not have articles like English a and the.

So Croatian simply says:

• moja sestra
• djecu
• u školu

Whether something is the children, children, the school, or a school is usually understood from context.

This is very normal in Croatian and other Slavic languages.

Yes. Croatian word order is much more flexible than English word order because case endings show each word’s role.

The sentence as given:

Moja sestra vodi djecu u školu.

is a very neutral, natural order: subject + verb + object + destination.

But other orders are possible for emphasis, for example:

• Djecu moja sestra vodi u školu.
  Emphasizes djecu.

• U školu moja sestra vodi djecu.
  Emphasizes u školu.

The basic meaning stays similar, but the focus changes.

Yes, if the context already makes it clear who is meant.

Croatian often omits subject pronouns and sometimes even subject nouns when they are understood.

So you could hear:

Vodi djecu u školu.

That could mean He/She is taking the children to school, depending on context.

In this full sentence, moja sestra is included to make the subject explicit and clear.