La supplente mette il registro sul banco prima che inizi la lezione.

Italian often drops subject pronouns when the verb ending already makes the subject clear. In mette, the ending tells you it is he/she puts.

So instead of saying Lei mette..., Italian very naturally says just La supplente mette... or even simply Mette... if the context is clear.

Supplente means a substitute teacher or supply teacher.

The article la shows that the teacher is female here.

• la supplente = a female substitute teacher
• il supplente = a male substitute teacher

Also, supplente can be both masculine and feminine; the article tells you the gender.

Mette is the third-person singular present tense of mettere.

Conjugation of mettere in the present:

• io metto
• tu metti
• lui/lei mette
• noi mettiamo
• voi mettete
• loro mettono

So la supplente mette means the substitute teacher puts.

Italian uses articles much more often than English does.

So where English might say puts the register or sometimes just puts down register/book, Italian normally says mette il registro.

Here il registro refers to a specific register, probably the classroom register or attendance book.

In a school context, registro usually means the class register, attendance book, or sometimes the grade book/class record.

It does not usually mean a language register in this sentence. The school context makes the meaning clear.

Sul is a contraction of su + il.

• su = on
• il banco = the desk

So:

• su il banco becomes sul banco

This kind of contraction is very common in Italian:

• a + il = al
• di + il = del
• in + il = nel
• su + il = sul

Banco usually means a school desk or student desk.

It is different from:

• tavolo = table
• scrivania = desk, usually an office desk
• cattedra = teacher’s desk or lectern

So sul banco suggests a school-type desk or classroom desk.

After prima che, Italian normally uses the subjunctive, not the indicative.

So:

• correct: prima che inizi la lezione
• not standard here: prima che inizia la lezione

This is one of the most important grammar points in the sentence.

Prima che means before, and it introduces a subordinate clause that normally requires the subjunctive.

Inizi is the present subjunctive of iniziare in the third-person singular.

Present subjunctive of iniziare:

• che io inizi
• che tu inizi
• che lui/lei inizi
• che noi iniziamo
• che voi iniziate
• che loro inizino

So prima che inizi la lezione means before the lesson begins.

Not in this exact sentence, if you keep the same structure.

Use prima di + infinitive when the subject is the same:

• La supplente mette il registro sul banco prima di iniziare la lezione. = The substitute teacher puts the register on the desk before starting the lesson.

Use prima che + subjunctive when a full clause follows:

• La supplente mette il registro sul banco prima che inizi la lezione. = The substitute teacher puts the register on the desk before the lesson begins.

So both are possible in some contexts, but the grammar structure changes.

Italian often uses the definite article where English may or may not use one.

Here la lezione refers to the lesson/class period in question, so the lesson is natural in Italian.

You will often see this with time-related or routine events:

• inizia la scuola
• finisce la partita
• comincia la riunione

Yes, Italian word order is fairly flexible, although the original sentence is very natural.

For example, you could also say:

• Prima che inizi la lezione, la supplente mette il registro sul banco.

This puts more emphasis on the time clause before the lesson begins.

The original version is probably the most neutral:

• La supplente mette il registro sul banco prima che inizi la lezione.

Yes. Italian uses the present tense both for actions happening now and for habitual actions.

So this sentence can mean:

• something happening right now in a narrative
• something that usually happens as part of classroom routine

That is very normal in Italian, just as in English:

• She puts the register on the desk before the lesson begins.

Yes, but the meaning changes slightly.

• l’insegnante = the teacher
• la supplente = the substitute teacher

So supplente is more specific. If the fact that she is a substitute teacher matters, la supplente is the better choice.

Also, insegnante can be masculine or feminine:

• l’insegnante can mean either a male or female teacher, depending on context.

Yes. Italian uses la lezione very naturally here.

Depending on context, English could translate it as:

• before the lesson begins
• before class starts

So the Italian wording is completely normal, even if English might choose different phrasing in a school context.