Learn Hardcore Norwegian: Barna lærer å resirkulere plast og papir på skolen. - The children learn to recycle plastic and paper at school.

So the definite plural is barna, not barnene.
Forms like guttene, jentene take -ene, but barn is different and must be memorized.

Why does Norwegian use lærer where English says are learning?

Norwegian usually uses the simple present for both English learn and are learning.

Barna lærer … can mean The children learn … or The children are learning …, depending on context.

Norwegian does have progressive forms with holder på å, but they are used less often than English -ing:

Barna holder på å lære å resirkulere … – The children are in the process of learning to recycle … (emphasizes the ongoing process)

What does the little word å do in lærer å resirkulere?

Å is the infinitive marker, like English to in to recycle.

å resirkulere – to recycle

Some verbs, like å lære, are usually followed by å plus an infinitive:

Barna lærer å lese. – The children are learning to read.
Barna lærer å resirkulere. – The children are learning to recycle.

So å here is required; Barna lærer resirkulere is ungrammatical.

Could you say Barna resirkulerer plast og papir på skolen instead?

Yes, but the meaning changes slightly:

Barna lærer å resirkulere plast og papir på skolen.
Focus: They are learning the skill of recycling.
Barna resirkulerer plast og papir på skolen.
Focus: They actually do the recycling at school (no explicit mention of learning).

So the original sentence specifically emphasizes the learning process.

Why is there no article before plast and papir?

Plast and papir are mass nouns here: they refer to materials in general, not specific pieces.

Norwegian, like English, usually drops the article with mass or generic materials:

De resirkulerer plast. – They recycle plastic.
Hun kjøper papir. – She buys paper.

You would only use a definite form when talking about specific, known plastic or paper:

De resirkulerer plasten fra kjøkkenet. – They recycle the plastic from the kitchen.

Could you say plastikk instead of plast?

You can say plastikk, but plast is more common and sounds more natural in modern Norwegian in this context.

plast – default everyday word for plastic (material)
plastikk – exists, but is used less; sometimes feels more technical or old-fashioned, depending on region and context.

In a school-recycling sentence, plast is the normal choice.

Why is it på skolen and not i skolen?

In Norwegian, på skolen is the standard expression for at school (as an institution / place of activity).

på skolen – at school (where they go to learn; general location of schooling)
i skolen – literally in the school (building); would usually sound odd here unless you are stressing the inside of the building in a very physical sense.

So:
Barna lærer … på skolen. – natural, idiomatic
Barna lærer … i skolen. – generally not idiomatic for this meaning.

Can på skolen be moved to the beginning of the sentence?

Yes. Norwegian has flexible word order for adverbials like på skolen, but the verb must stay in second position (the V2 rule):

Barna lærer å resirkulere plast og papir på skolen. (neutral)
På skolen lærer barna å resirkulere plast og papir. (emphasis on at school)

Both are correct. Moving på skolen to the front puts extra focus on the location.

Why is lærer both learns and teacher?

The word lærer can be:

A verb form:
- From å lære – to learn / to teach
- Barna lærer … – The children learn / are learning …
A noun:
- en lærer – a teacher
- læreren – the teacher

They are distinguished by context and by pronunciation (in normal speech, the noun often has a slightly different stress and length), but in writing they look the same.

How would this sentence look in the past or future?

The verb å lære is regular:

Present: lærer – learn / are learning
Past: lærte – learned / were learning
Present perfect: har lært – have learned / have been learning

Using the same sentence:

Past simple:
Barna lærte å resirkulere plast og papir på skolen. – The children learned to recycle …
Present perfect:
Barna har lært å resirkulere plast og papir på skolen. – The children have learned to recycle …

For future, Norwegian often uses skal or kommer til å:

Barna skal lære å resirkulere plast og papir på skolen. – The children will / are going to learn …

Could you say Barna lærer seg å resirkulere plast og papir på skolen?

Yes, lære seg is possible, but it adds a nuance:

lære – focus on the teaching/learning process in general
lære seg – learn for oneself, pick up a skill; a bit more reflexive/personal

In this context:

Barna lærer å resirkulere … – neutral; they are being taught to recycle.
Barna lærer seg å resirkulere … – they are in the process of acquiring this skill themselves; possibly a bit more emphasis on them mastering it.

Both are grammatical; lærer without seg is more neutral and common in general statements like this.

Why is there only one å even though there are several verbs in English (learn to recycle)?

In Norwegian, you only need å directly in front of the infinitive verb:

lære å resirkulere – learn to recycle

You do not repeat å after lære, because lære itself is a finite verb in the present tense (lærer), and å only goes before the infinitive resirkulere.

So:

Correct: Barna lærer å resirkulere …
Incorrect: Barna lærer å å resirkulere …

Why is the word order resirkulere plast og papir, not resirkulere plasten og papiret?

The original sentence talks about recycling plastic and paper in general, not specific items:

resirkulere plast og papir – recycle plastic and paper (as types of waste)
resirkulere plasten og papiret – recycle the plastic and the paper (specific, known plastic and paper)

In a general statement about what children learn at school, the generic, article-less form is the most natural and idiomatic.

Could you swap the order and say papir og plast instead of plast og papir?

Yes, grammatically you can say either:

Barna lærer å resirkulere plast og papir …
Barna lærer å resirkulere papir og plast …

The difference is minimal; plast og papir might sound slightly more fixed or familiar because that order is common in recycling contexts, but both are correct and natural.