Parentes dicunt disciplinam in schola et in domo utilem esse.

Because after dicunt here, Latin uses an indirect statement construction.

With verbs like dico meaning say, Latin often says:

subject of the reported statement + infinitive

So instead of using a word like that, Latin puts the subject of the reported statement into the accusative.

That is why we get:

Parentes dicunt disciplinam ... utilem esse

Literally, this is something like:

The parents say discipline ... to be useful

So disciplinam is accusative because it is the subject of esse inside the indirect statement.

Because utilem agrees with disciplinam.

Even though disciplinam is the logical subject of esse, it is still in the accusative because of the indirect statement. Any adjective describing it must match it in:

• gender
• number
• case

disciplina is:

• feminine
• singular

and here, in the indirect statement, it is:

• accusative singular

So the adjective must also be feminine accusative singular:

• masculine/feminine nominative singular: utilis
• neuter nominative singular: utile
• masculine/feminine accusative singular: utilem

So utilem is exactly the form we expect.

Because this sentence is using indirect statement, not a direct statement.

A direct statement would be:

Disciplina in schola et in domo utilis est.
Discipline is useful at school and at home.

But after dicunt, Latin changes the reported clause into:

• accusative subject: disciplinam
• infinitive verb: esse

So:

Parentes dicunt disciplinam in schola et in domo utilem esse.

In other words, est becomes esse in this kind of construction.

Because Latin usually does not use a conjunction like that after verbs of saying, thinking, knowing, hearing, and so on.

English says:

The parents say that discipline is useful.

Latin usually says:

The parents say discipline to be useful.

That sounds unnatural in English, but it is normal in Latin. This is the accusative-and-infinitive construction, often abbreviated as ACI.

So the idea of that is there in the meaning, but Latin expresses it through grammar rather than with a separate word.

They are both in the ablative, because in with the ablative often means in or at a place.

So:

• in schola = in school / at school
• in domo = in the home / at home

Here the sentence is talking about location, not motion toward a place. If there were motion into a place, Latin would usually use in with the accusative instead.

Domus is a somewhat irregular noun. It mixes forms from different declensions.

Its ablative singular can be domo, which is the form used here after in.

So even though the dictionary form is domus, the phrase in domo is perfectly normal Latin.

This is a good phrase to memorize as a set expression:

• in domo = at home / in the house

Latin often repeats the preposition with each noun:

in schola et in domo

This makes the structure clear and balanced.

Sometimes Latin can omit the second preposition if the meaning is obvious, but repeating it is very common and often sounds more natural, especially in a simple teaching sentence like this one.

So here the repeated in is not strange at all.

The subject is parentes.

Parentes is nominative plural, and dicunt is third person plural, so they match:

• parentes = parents
• dicunt = they say

So the basic frame is:

Parentes dicunt = The parents say

Then everything after that is what they say.

Disciplina can mean several related things in Latin, such as:

• discipline
• instruction
• training
• education

In this sentence, the exact English translation depends on the context already given to the learner, but grammatically it is a feminine singular noun.

A learner should know that Latin words often cover a broader range of meanings than one single English word. So disciplina is not always only discipline in the modern English sense of punishment or strict behavior; it can also refer more broadly to training or instruction.

Not as much as in English.

Latin word order is relatively flexible because the endings show the grammatical roles. So the sentence could be rearranged in different ways without changing the basic meaning.

For example, Latin keeps the meaning clear because:

• parentes is nominative
• disciplinam is accusative
• utilem matches disciplinam
• esse is the infinitive of the indirect statement

That said, the given order is very natural:

• Parentes dicunt first gives the main statement
• then comes the reported idea
• esse comes at the end, which is common in Latin

So the word order is flexible, but not random.

Yes. That is a very useful way to understand it.

The indirect statement is:

Parentes dicunt disciplinam in schola et in domo utilem esse.

The corresponding direct statement would be:

Disciplina in schola et in domo utilis est.

Notice the changes:

• disciplinam becomes disciplina
• utilem becomes utilis
• esse becomes est

That is a great pattern to practice, because it helps you see how Latin changes a normal statement into reported speech.

Yes. It is best to read it as a single grammatical chunk.

After dicunt, the whole phrase

disciplinam in schola et in domo utilem esse

functions as the content of what the parents say.

Inside that chunk:

• disciplinam is the subject of the infinitive
• utilem describes disciplinam
• esse is the verb
• in schola et in domo tells where it is useful

So when reading, it helps not to separate disciplinam too much from utilem esse. They belong together as part of the indirect statement.