Kad izađeš iz škole, nazovi me.

Both kad and kada mean when.

• kad is the shorter, very common everyday form
• kada is a bit fuller and can sound slightly more formal or emphatic

So in this sentence, Kad izađeš iz škole, nazovi me. is completely natural. You could also say Kada izađeš iz škole, nazovi me. with essentially the same meaning.

Yes, izađeš looks like a present-tense form, but here it is used in a clause referring to the future.

It comes from the verb izaći = to go out / to come out / to leave.

Croatian often uses the present tense of a perfective verb after words like kad to talk about a future completed action:

• Kad dođeš, javi se. = When you arrive, let me know.
• Kad završiš, nazovi me. = When you finish, call me.

So kad izađeš means something like when you get out / once you leave.

The base verb is izaći.

This is one of those verbs whose present-tense forms do not look exactly like the infinitive. That is very common in Croatian.

Some forms are:

• ja izađem
• ti izađeš
• on/ona/ono izađe
• mi izađemo
• vi izađete
• oni/one/ona izađu

So izađeš means you go out / you leave.

After the preposition iz (out of / from), Croatian uses the genitive case.

So:

• škola = nominative singular
• iz škole = genitive singular

This is why the ending changes from -a to -e.

A few similar examples:

• iz kuće = out of the house
• iz grada = out of the city
• iz sobe = out of the room

This is a very common learner question.

• iz usually means out of / from inside
• s(a) usually means off / from a surface or sometimes from in other contexts

So:

• iz škole = out of school / from school
• iz kuće = out of the house
• sa stola = off the table
• s posla = from work

With škola, Croatian naturally uses iz škole.

Yes. Nazovi is the imperative form of nazvati = to call.

It means call! when speaking to one person informally (ti).

So:

• nazovi me = call me

Other related forms:

• nazovite me = call me (to more than one person, or formal singular/plural)
• zovi me = call me / keep calling me / call me regularly, depending on context

This is mainly about aspect.

• nazvati is perfective
• zvati is imperfective

So:

• nazovi me usually means give me a call / call me once
• zovi me can mean call me, but often with a more ongoing, repeated, or less bounded feel

In this sentence, nazovi me is the natural choice because it refers to one completed call after you leave school.

Here me is the unstressed accusative clitic form of ja.

After nazvati (to call someone), the person being called is a direct object, so Croatian uses the accusative:

• nazovi me = call me

Compare:

• me = me (short unstressed accusative/genitive form)
• mene = me (full/emphatic accusative/genitive form)
• meni = to me (dative)

So:

• Nazovi me. = Call me.
• Nazovi mene, a ne njega. = Call me, not him.
  Here mene is used for emphasis.
• Daj meni knjigu. = Give the book to me.

Because me is a clitic: a short unstressed word that tends to go in a fixed position in the clause, usually near the beginning of its clause, but not as the very first word.

In an imperative like this, putting the clitic after the imperative verb is normal:

• Nazovi me.
• Javi mi se.
• Donesi ga.

So nazovi me is the standard word order.

The comma separates the dependent clause from the main clause.

• Kad izađeš iz škole = subordinate time clause
• nazovi me = main clause

So Croatian writes:

Kad izađeš iz škole, nazovi me.

This is similar to English writing: When you leave school, call me.

It can depend on context.

iz škole can mean:

• physically out of the school building
• from school in the everyday sense of finishing classes and leaving

In ordinary conversation, this phrase often simply means when you get out of school / when school is over for you.

Grammatically yes, but it changes the meaning a bit.

• nazovi me = call me, usually by phone
• pozovi me = call/invite/summon me, depending on context

If you specifically mean phone me, nazovi me is the best choice.

It is informal, because it uses:

• izađeš = you singular informal (ti)
• nazovi = imperative for ti

If you wanted the formal or plural version, you would say:

Kad izađete iz škole, nazovite me.

That can mean:

• speaking to several people, or
• speaking politely/formally to one person

A natural pronunciation would sound roughly like:

Kad izađeš iz škole, nazovi me.

A few useful notes:

• dž in izađeš sounds like the j in jam
• š sounds like sh
• č / ć are different sounds in Croatian, though many learners take time to hear the difference clearly
• z in nazovi is a normal z sound

You do not need to master the pitch accent system to say this sentence understandably. Clear consonants and vowels are much more important at this stage.