Durante o recreio, os alunos falam alto, mas no intervalo da prova todos ficam quietos.

They can both refer to a break, but they are used a little differently.

• recreio usually means recess, especially in a school context
• intervalo means interval, break, or pause between parts of something

So here:

• Durante o recreio = during recess
• no intervalo da prova = in the break during the test / during a pause in the test context

In Brazilian Portuguese, recreio sounds more specifically like school recess, while intervalo is more general.

Durante means during.

It is used to show that something happens within a period of time:

• Durante o recreio = during recess
• durante a aula = during class
• durante o filme = during the movie

It does not change form here. It is simply a preposition.

Portuguese uses definite articles much more often than English.

• os alunos = the students
• alunos = students

Even when English would naturally say just students, Portuguese often prefers os alunos if it means a specific or understood group.

So os alunos falam alto sounds very natural in Portuguese.

These are present tense forms for they.

• falam comes from falar = to speak
• ficam comes from ficar = to become, to stay, to remain

Conjugation:

• ele/ela fala = he/she speaks

• eles/elas falam = they speak

• ele/ela fica = he/she becomes/stays
• eles/elas ficam = they become/stay

The subjects are plural:

• os alunos → falam
• todos → ficam

Yes, alto often means high or tall, but with verbs like falar, it can mean loudly.

So:

• falar alto = to speak loudly
• falar baixo = to speak softly / quietly

This is very common in Portuguese. Instead of using an adverb ending like English loudly, Portuguese often uses an adjective-like form after the verb:

• Ela fala baixo. = She speaks softly.
• Eles falam alto. = They speak loudly.

Because ficar here means to become or to stay in a certain state.

• ficar quieto = to become quiet / to stay quiet
• ser quieto = to be a quiet person by nature

So:

• todos ficam quietos = everyone becomes/stays quiet
• todos são quietos = everyone is quiet by nature

In this sentence, the idea is about behavior in that moment, not personality, so ficam quietos is the natural choice.

Because it agrees with todos, which is plural.

• todo fica quieto = each one becomes quiet / everyone becomes quiet in a singular-style idea
• todos ficam quietos = everyone / all of them become quiet

Agreement in Portuguese:

• masculine singular: quieto
• feminine singular: quieta
• masculine plural: quietos
• feminine plural: quietas

Since todos refers to a mixed group or a group of males, quietos is used.

Todos means everyone or all of them, depending on context.

In this sentence, it refers to the students as a group:

• todos ficam quietos = everyone becomes quiet

Grammatically, todos is plural, so the verb is also plural:

• todos ficam not
• todos fica

This is a contraction.

• em + o = no
• de + a = da

So:

• no intervalo = em o intervalo = in the break
• da prova = de a prova = of the test

Putting it together:

• no intervalo da prova = in the break of the test / during the test break

These contractions are extremely common in Portuguese and are required in standard usage.

Mas means but.

It connects two contrasting ideas:

• during recess, the students speak loudly
• but during the test break, everyone stays quiet

So mas introduces the contrast between noisy behavior and quiet behavior.

Be careful not to confuse:

• mas = but
• mais = more

Yes, literally it is of the test, and it is natural in Portuguese.

Portuguese often uses de structures where English might prefer another phrasing.

Examples:

• o início da aula = the beginning of class
• o fim do filme = the end of the movie
• o intervalo da prova = the break of the test / the test break

In natural English, you might translate it more freely, but in Portuguese the de + noun structure is very common.

Not with the same meaning.

• na prova = on the test / in the test
• no intervalo da prova = during the break in the test context

If you say:

• Na prova, todos ficam quietos.

that means During the test, everyone stays quiet, which is a bit different from saying they are quiet in the break or interval related to the test.

The comma separates the introductory time phrase from the main clause:

• Durante o recreio, os alunos falam alto

This is similar to English punctuation in sentences like:

• During recess, the students speak loudly.

The comma is helpful and natural here, especially because the sentence begins with a prepositional phrase.

The original sentence is already natural, but in casual spoken Brazilian Portuguese, people might say things like:

• No recreio, os alunos falam alto, mas na prova todo mundo fica quieto.
• Durante o recreio, a turma fala alto, mas no intervalo da prova fica todo mundo quieto.

Some differences:

• No recreio is a bit simpler than Durante o recreio
• todo mundo is more conversational than todos
• a turma can mean the class/group

The original sentence, though, is clear and standard.

A rough English-style guide is:

• re-crei-o

The stressed part is usually crei.

A very approximate pronunciation for English speakers is:

• heh-KRAY-oh or reh-KRAY-oh, depending on accent

A few notes:

• the r at the beginning can sound like an English h in many Brazilian accents
• ei sounds like the ay in say

Yes, quietos can be tricky for English speakers.

A rough guide is:

• qui-e-tos

Approximate sound:

• kee-EH-tos

Important details:

• quie is not one single English-like sound
• the word has a clear separation: qui-e
• the stress is usually on e: qui-E-tos

Take it slowly at first:

• qui
• e
• tos

Then combine them:

• qui-e-tos

Yes. In this sentence, both help describe behavior or state.

• falam alto = they speak loudly
• ficam quietos = they become/stay quiet

But grammatically they work a bit differently:

• alto functions like an adverbial expression after falar
• quietos is an adjective agreeing with the subject after ficar

So they both describe what is happening, but they are not exactly the same type of word in the sentence.

It has two main parts joined by mas:

1. Durante o recreio, os alunos falam alto

   • time expression: Durante o recreio
   • subject: os alunos
   • verb: falam
   • complement: alto

2. mas no intervalo da prova todos ficam quietos

   • connector: mas
   • time/place expression: no intervalo da prova
   • subject: todos
   • verb: ficam
   • predicate adjective: quietos

This is a very useful Portuguese pattern:

• During X, subject + verb..., but in Y, subject + verb...