De school begint in augustus.

Because school is a de-word in Dutch. Nouns in Dutch take either de or het, and this is something you usually have to learn with each noun.

So:

• de school = the school

There is no special rule here that would make it het.

Begint is the third person singular form of the verb beginnen (to begin).

The subject is de school, which is grammatically it / the school, so Dutch uses the hij/zij/het form:

• ik begin = I begin
• jij begint = you begin
• de school begint = the school begins

So the -t is just the normal present-tense ending for third person singular.

Dutch main clauses usually follow the V2 rule: the finite verb goes in the second position.

In this sentence:

• De school = first position
• begint = second position
• in augustus = the rest

So De school begint in augustus has normal Dutch word order.

Dutch normally uses in with months.

Examples:

• in augustus = in August
• in januari = in January
• in de zomer = in the summer

So this works just like English in August.

In Dutch, names of months are normally written with a lowercase letter.

So:

• augustus
• september
• januari

This is different from English, where August and September are capitalized.

Not really. Dutch often uses school to refer to school as an institution or the school term / school year, not just the physical building.

So in context, this sentence is understood as something like:

• school starts in August
• the school year begins in August

This kind of usage is very natural in Dutch.

Sometimes, yes, but it changes the feel a little.

• De school begint in augustus sounds more like a regular complete sentence with the school as the subject.
• School begint in augustus can sound more general or institutional, like school starts in August.

Dutch sometimes drops the article in expressions involving institutions, but for learners, de school begint in augustus is a safe and clear form.

They are very close in meaning.

• beginnen = to begin
• starten = to start

In many contexts, both can work:

• De school begint in augustus
• De school start in augustus

But beginnen is often the more neutral, everyday verb here.

The dictionary form is beginnen.

This is the infinitive form, the form you would look up in a dictionary.

So:

• sentence form: begint
• dictionary form: beginnen

A rough English-friendly guide is:

• de ≈ duh
• school ≈ skhole (with the Dutch sch sound, not exactly like English)
• begint ≈ buh-GINT
• in = in
• augustus ≈ ow-GUS-tus

A few pronunciation notes:

• sch in school is not exactly English sk; in standard Dutch it has a harsher sound.
• The g in begint and augustus is the Dutch g/ch sound, which is much rougher than the English g in go.

Yes. The Dutch present tense can do both.

So De school begint in augustus can mean:

• a general fact: school begins in August
• a scheduled future event: the school starts in August

Dutch often uses the present tense for planned or scheduled future events, just like English does in sentences such as School starts in August.