Magistra respondet se idem consilium iam proposuisse, sed discipulos antea paratos non fuisse.

Because se is the reflexive pronoun, and it refers back to the subject of the main verb, magistra.

So:

• Magistra respondet = the teacher replies
• se ... proposuisse = that she herself had proposed ...

If Latin used eam instead, it would normally mean her as someone else, not the teacher.

After a verb like respondet, Latin often uses indirect statement, also called the accusative-and-infinitive construction.

Instead of using a clause with that + a finite verb, Latin often does this:

• accusative subject + infinitive

So here:

• se idem consilium iam proposuisse = that she had already proposed the same plan
• discipulos antea paratos non fuisse = that the students had not been ready before

This is one of the most important sentence patterns in Latin.

In an indirect statement, the subject goes into the accusative.

So:

• se is the subject of proposuisse
• discipulos is the subject of fuisse

Even though both are accusative forms, they are not direct objects here. They are the logical subjects of the infinitives.

Because they are perfect infinitives.

A perfect infinitive usually shows action that happened before the action of the main verb. So the sequence is:

• respondet = she replies
• proposuisse = to have proposed earlier
• fuisse = to have been earlier

So Latin is showing that both the proposing and the students’ lack of readiness happened before the moment of replying.

In English, this often gets translated with had proposed and had been, though sometimes context may allow slightly different wording.

Because idem has to agree with consilium.

• consilium is neuter singular accusative
• the matching form of idem, eadem, idem is idem

For neuter singular, the nominative and accusative are the same, so idem is correct here.

So idem consilium means the same plan.

Consilium is accusative singular.

It is the direct object of proposuisse:

• proponere consilium = to propose a plan

So in se idem consilium iam proposuisse, the teacher is the subject of the infinitive clause, and idem consilium is what she proposed.

Because it agrees with discipulos, which is also accusative plural masculine.

In the clause:

• discipulos ... paratos non fuisse

discipulos is the subject of the infinitive fuisse, and paratos is a predicate adjective describing them.

Since the subject of an indirect statement is accusative, any adjective agreeing with it is also accusative.

So:

• discipulos = the students
• paratos = ready

Both are masculine plural accusative.

Both are adverbs, but they do different jobs.

• iam = already, by now
• antea = before, earlier, beforehand

So:

• iam proposuisse suggests that the teacher had already proposed the plan
• antea paratos non fuisse says that the students had not been ready earlier / beforehand

They help show the timing and the contrast between the two parts of the sentence.

Yes.

The verb respondet governs both parts:

• se idem consilium iam proposuisse
• sed discipulos antea paratos non fuisse

So the full sense is:

• the teacher replies that she had already proposed the same plan,
• but that the students had not been ready earlier

Latin does not need to repeat a separate word for that, because the accusative-and-infinitive construction already shows reported statement.

Latin word order is much more flexible than English word order, because the endings show the grammatical relationships.

This sentence is arranged in a way that highlights the structure and contrast:

• Magistra respondet sets up the reporting verb first
• se ... proposuisse gives the first reported statement
• sed introduces the contrast
• discipulos ... non fuisse gives the second reported statement

Also:

• iam is placed near proposuisse
• antea is placed near the idea of the students’ readiness
• non stands before fuisse, negating the clause

So the order is not random; it helps emphasize the contrast between what the teacher had done and what the students had not been.

In normal classical prose after respondet, Latin strongly prefers the indirect statement construction, so the infinitives are the standard way to say it.

A learner might want to turn it into something like:

• the teacher replies that she already proposed...
• but that the students were not ready...

That is a natural English pattern, but Latin usually expresses that meaning with:

• accusative subject
• infinitive verb

So the infinitives are not unusual here; they are exactly what you should expect after a verb of saying or answering.