Learn Hardcore Norwegian: Læreren sier at vi skal lære av hverandre i dag. - The teacher says that we shall learn from each other today.

At introduces a content clause (a “that”-clause). Som is a relative pronoun meaning “who/that/which” in relative clauses. After verbs like si(e), tro, mene, vite, you normally use at to introduce what is said, thought, etc.

What happens to word order after at? Does Norwegian still use V2?

No. V2 (finite verb in second position) applies to main clauses, not to clauses introduced by at. In an at-clause, the typical order is:

at + subject + (adverbs like ikke) + finite verb + non-finite verb + ... In the sentence, that gives at vi skal lære ... (subject vi before the finite verb skal).

Where would ikke go if I wanted to negate the clause?

Main clause: Vi skal ikke lære ...
Subordinate clause: at vi ikke skal lære ... In subordinate clauses, ikke comes before the finite verb.

Why is there no å before lære after skal?

Modal verbs drop å before the infinitive. Common modals: skal, vil, kan, må, bør (and their past forms skulle, ville, kunne, måtte, burde).

vi skal lære, vi kan lære, not vi skal å lære.

What nuance does skal have compared to vil or kommer til å?

skal: plan/arrangement, obligation, or strong intention.
vil: want/wish or tendency.
kommer til å: neutral prediction. All can refer to future, but the nuance differs.

How do I say this in the past (reported speech)?

Use the preterite of both the reporting verb and the modal:

Læreren sa at vi skulle lære av hverandre i dag.

Why is it lære av and not lære fra?

Use lære av (noen/noe) to mean “learn from (someone/something)” in the sense of drawing lessons from a source.

lære av feilene sine, lære av hverandre Fra is for origin/direction (“from a place”) and in the fixed phrase lære fra seg (“to teach, pass on knowledge”). Lære fra (noen) for “learn from” is not standard.

Does av hverandre mean the same as fra hverandre?

No.

av hverandre = from one another (as a source of learning/influence).
fra hverandre = apart from each other/away from each other (spatial or separation).

How is hverandre used? Can it be used for groups larger than two?

Hverandre is a reciprocal pronoun meaning “each other,” used for two or more people.

Object: lære av hverandre
Possessive form: hverandres (preferred in writing): Vi respekterer hverandres meninger. Colloquial: hverandre sine is common in speech but less formal.

Can I drop at like English sometimes drops “that”?

Generally no in standard written Norwegian. Keep at after verbs like sier. In informal speech some dialects may drop it, but you should include it in writing.

Where else can I put i dag? Does its position change the meaning?

All are possible, with slight differences in focus/scope:

I dag sier læreren at vi skal lære av hverandre. (Today, the teacher says that…)
Læreren sier i dag at vi skal lære av hverandre. (It is today that the saying occurs.)
Læreren sier at vi i dag skal lære av hverandre. (It is today that the learning will happen.)

Is i dag one word or two?

Two words in Bokmål: i dag. Similarly: i morgen, i går. The single-word form idag is non-standard in Bokmål.

Should there be a comma before at?

Normally no comma before at in a sentence like this. Norwegian does not mirror English comma rules here. Commas are used to set off parenthetical subordinate clauses, not simply before at by default.

What’s the difference between sier, sier til, and forteller?

sier at ... = says that ...
sier til (noen) at ... = says to (someone) that ...
forteller (noen) at ... = tells (someone) that ... If you name the person addressed, use til or forteller: Læreren sier til oss at ... / Læreren forteller oss at ...

Does lære mean both “learn” and “teach”?

Yes, context decides:

Intransitive: å lære = to learn.
Transitive: å lære noen noe = to teach someone something. Common teaching verbs: lære bort, lære fra seg (to teach/pass on knowledge).

Any quick pronunciation tips for the tricky parts?

æ in Læreren is like the vowel in English “cat,” often a bit longer.
In hverandre, the h in hv is silent; you hear a v sound at the start.
Final -en in læreren is typically a reduced vowel.
sk in skal is plain [sk], not the sj sound.