Parentes dicunt bonos mores in domo et in schola servandos esse.

The sentence has two parts:

Parentes dicunt
= The parents say

Then comes what they say, expressed as an indirect statement:

bonos mores in domo et in schola servandos esse
= that good morals / good behavior must be observed at home and at school

So the main verb is dicunt, and everything after it is the content of the statement.

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

Instead, Latin normally uses an accusative + infinitive construction:

• dicunt = they say
• bonos mores ... esse = good morals ... to be

This is the standard Latin way to express reported speech or reported thought.

In an indirect statement, the subject of the reported idea goes into the accusative.

If this were a direct statement, you would expect:

boni mores servandi sunt
= good morals must be observed

But after dicunt, Latin changes that reported subject into the accusative:

bonos mores servandos esse

So bonos mores is accusative because it is the subject of the infinitive construction after dicunt.

Servandos esse is a form of the passive periphrastic, which expresses necessity or obligation.

It comes from:

• servare = to keep, preserve, observe
• servandus, -a, -um = needing to be kept / to be observed
• esse = to be

So servandos esse means something like:

to have to be observed
or more natural English, must be observed

Because the sentence is in indirect statement after dicunt, Latin uses esse rather than a finite verb such as sunt.

Because both words agree with mores.

• bonos describes mores
• servandos also refers to mores

Since mores is masculine plural accusative here, both of those words must match it in:

• gender: masculine
• number: plural
• case: accusative

This kind of agreement is very important in Latin.

Mores is the plural of mos, moris.

Depending on context, mores can mean:

• manners
• morals
• habits
• customs
• behavior

In this sentence, it most likely means good morals or good behavior.

Latin very often uses the plural mores where English may use a singular idea such as character or a collective idea such as behavior. So the plural here is normal Latin usage.

They are both in the ablative because in with the ablative usually indicates location:

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

Latin uses:

• in
  • ablative for where
• in
  • accusative for into where, meaning motion toward

So:

• in schola = at school
• in scholam = into the school

Here the meaning is location, not motion, so the ablative is used.

Yes. Latin often uses domi to mean at home.

So a learner might expect domi et in schola.

But in domo is also perfectly understandable and means literally in the house. It can sound a little more concrete or spatial than domi. So the sentence as given is fine; it just uses a regular in + ablative phrase.

The sentence does not explicitly say who has the obligation. Latin can leave that unstated when the sense is general.

So the idea is something like:

good morals must be observed at home and at school

This can imply a general obligation for children, students, people in the household, or people in those settings. If Latin wanted to name the person who has the duty, it could add a dative, as in a fuller passive periphrastic construction.

Yes. Although servare can mean to save, to preserve, or to keep, it can also mean to keep to, to maintain, or to observe.

With something like mores, the sense is:

• to keep good morals
• to maintain good behavior
• to observe proper conduct

So bonos mores servare is a very natural Latin idea.

A direct version would be:

Boni mores in domo et in schola servandi sunt.

That means:

Good morals must be observed at home and at school.

Then after dicunt, Latin changes it into indirect statement:

• boni mores becomes bonos mores
• servandi sunt becomes servandos esse

So:

Parentes dicunt bonos mores in domo et in schola servandos esse.