Learn Hardcore Czech: U školy se ráno nesmí parkovat, protože tam jsou děti. - In the morning you are not allowed to park at the school because there are children there.

u školy – “by the school, near the school.”
Emphasis: the area around the building (e.g. curbside, street next to it).
ve škole – “in(side) the school.”
Refers to the interior (corridors, classrooms, building interior).
před školou – “in front of the school.”
More specific location: in the area directly in front of the entrance / front side.

For a sign about not parking near the building, u školy or před školou is natural; ve škole would sound strange for parking, because you don’t normally park inside the building.

What does se do in u školy se ráno nesmí parkovat?

Here se creates an impersonal “se-passive” construction:

nesmí se parkovat ≈ “parking is not allowed” / “one must not park.”

No specific subject (“you, people, drivers”) is mentioned; the rule is presented in a general, impersonal way.

Structurally:

smět = “to be allowed, may”
nesmí se + infinitive = “it is not allowed to … / one must not …”

So se is not reflexive in the usual “myself/yourself” sense; it’s a marker of an impersonal rule.

Why say se nesmí parkovat instead of nesmíte parkovat?

Both are grammatically correct, but they differ in tone and focus:

U školy se ráno nesmí parkovat.
– General rule, impersonal: “Parking by the school in the morning is not allowed.”
– Typical for signs, regulations, official wording.
U školy ráno nesmíte parkovat.
– Directly addresses you (plural or formal singular): “You must not park by the school in the morning.”
– Sounds more like a person speaking to specific listeners.

In written rules and signs, Czech strongly prefers the impersonal nesmí se parkovat style.

What exactly does nesmí mean compared to nemůže?

Both are negatives, but they differ:

smět / nesmět = may / may not, be allowed / not be allowed
- nesmí = “must not, is not allowed to.”
moci / nemoci = can / cannot, be able / not be able
- nemůže = “cannot, is not able to” (for practical or physical reasons).

So:

U školy se ráno nesmí parkovat.
– It is forbidden by rule.
U školy se ráno nemůže parkovat.
– Suggests it is not possible (e.g. road is blocked, no space), not primarily about a legal/official ban.
– This sounds odd as a “rule” sentence; nesmí is the natural choice.

Why is ráno used alone to mean “in the morning” without a preposition like in?

Czech often uses bare time adverbs for parts of the day:

ráno – in the morning
večer – in the evening
odpoledne – in the afternoon
v noci – at night (this one usually takes v, but is a bit special)

So ráno by itself commonly means “in the morning”.
You don’t say ✗ v ráno in standard Czech in this meaning.

In your sentence:

se ráno nesmí parkovat = “it is not allowed to park in the morning.”

Can I change the word order? For example, say Ráno se u školy nesmí parkovat?

Yes, Czech word order is quite flexible. All of these are correct:

U školy se ráno nesmí parkovat.
Ráno se u školy nesmí parkovat.
U školy ráno se nesmí parkovat. (less usual, but possible)
Nesmí se ráno parkovat u školy. (more neutral in speech)

The meaning stays the same, but the emphasis changes:

Starting with Ráno stresses the time: “In the morning, (specifically then) you must not park by the school.”
Starting with U školy stresses the place: “By the school, (specifically there) you must not park in the morning.”

The original order is very natural for a neutral statement or sign.

Why is parkovat in the infinitive? Could we use a noun like parkování?

The structure (ne)smí se + infinitive is standard for expressing what is or isn’t allowed:

Smí se parkovat. – “Parking is allowed.”
Nesmí se parkovat. – “Parking is not allowed.”

Using the noun parkování is also possible but sounds more formal or sign-like, and you’d usually use a different structure:

Parkování u školy je ráno zakázáno.
– “Parking by the school is prohibited in the morning.”

So:

nesmí se parkovat – natural, everyday phrasing of a rule.
parkování je zakázáno – more formal / administrative style.

Why is it parkovat (imperfective) and not zaparkovat (perfective)?

Parkovat is imperfective; zaparkovat is perfective.

parkovat – the general activity of parking (process/state).
zaparkovat – to complete the act, to “manage to park” once.

General rules about what is allowed or forbidden use imperfective:

Tady se nesmí kouřit. – Smoking is not allowed here.
Zde se nesmí přecházet. – Crossing here is not allowed.
U školy se ráno nesmí parkovat. – Parking by the school in the morning is not allowed.

Using zaparkovat would incorrectly make it sound like “You are not allowed to successfully park once,” which is not how such rules are expressed.

Why do we say protože tam jsou děti and not just protože jsou děti?

The word tam means “there” and points back to the place already mentioned (u školy).

protože tam jsou děti – “because there are children there (in that place near the school).”

You can say protože jsou tam děti (same words, different order), but:

Dropping tam entirely — protože jsou děti — is usually incomplete: “because there are children…” (where? it feels unfinished unless context is very clear).

So tam anchors the reason to the location in the first clause: “at that spot, there are children.”

Can the word order in protože tam jsou děti change? For example, protože jsou tam děti?

Yes, both are correct:

protože tam jsou děti
protože jsou tam děti

The difference is subtle:

protože tam jsou děti – puts a little more emphasis on tam (the location).
protože jsou tam děti – more neutral; tam just tags along with jsou.

In everyday speech, protože jsou tam děti is probably a bit more common, but both are natural.

Why is děti used like this? Is it plural, and does the form change?

Děti is the plural form of dítě (“child”).
It’s a bit irregular:

1 child – dítě
2+ children – děti

In the nominative plural (subject form), it is děti.
In the accusative plural (direct object), it is also ději.

So in tam jsou děti:

děti is nominative plural (subject of jsou = “are”).

The same form is used in several cases, which can be confusing for learners, but here it’s simply the subject: “children are there.”

Is protože the only word for “because”? How does it compare to jelikož or poněvadž?

Czech has several conjunctions meaning “because”:

protože – the most common, neutral, all-purpose “because.”
jelikož – more formal/literary; often used in written texts, sounds a bit elevated.
poněvadž – somewhat old-fashioned or literary in many regions.

In your sentence, protože is by far the most natural choice:

U školy se ráno nesmí parkovat, protože tam jsou děti.

You could replace it with jelikož in a formal text:

… jelikož tam jsou děti.

…but for everyday speech and normal writing, stick with protože.

Could you translate the whole sentence more literally and also in a natural way into English?

A fairly literal translation:

“By the school, in the morning, (it) must not be parked, because there are children there.”

A natural English version:

“You must not park by the school in the morning, because there are children there.”
or
“Parking by the school in the morning is not allowed because there are children there.”