У вересні я йду до школи.

Because after у / в when you talk about a time period like in September, Ukrainian uses the locative case.

So:

• вересень = September
• у вересні = in September

This is a very common pattern with month names:

• у січні = in January
• у березні = in March
• у жовтні = in October

So вересні is not a different word; it is the locative form of вересень.

Both у and в can mean in. Ukrainian often chooses between them for euphony, meaning whatever sounds smoother.

Here, у вересні is preferred because в вересні would put a в right before another в sound, which is awkward to pronounce.

So the choice is mainly about sound, not meaning:

• у вересні = natural and smooth
• в вересні = possible in theory, but not the usual choice here

In Ukrainian, months are normally written with a lowercase letter, unlike in English.

So:

• вересень = September
• січень = January
• липень = July

They are only capitalized if they begin a sentence or are part of a title.

Йду is the 1st person singular form of йти, which means to go on foot.

So:

• я йду = I go / I am going

The verb йти is used for movement in one direction or for a specific trip. That is why it appears in a sentence about going somewhere.

This is a very important Ukrainian distinction.

• йти / йду = to go, be going in one direction, one specific trip
• ходити / ходжу = to go habitually, repeatedly, back and forth

So:

• Я йду до школи. = I am going to school / I’m on my way to school
• Я ходжу до школи. = I go to school / I attend school regularly

In your sentence, йду suggests a specific going-to-school event or a planned movement, not a general habit.

Grammatically, йду is a present-tense form. But in Ukrainian, present tense can sometimes be used for a planned or expected future action, especially when there is a clear time expression.

Here, У вересні gives that time frame, so the sentence can mean something like:

• In September I’m going to school
• In September I will go to school

This is similar to English sentences like I’m leaving tomorrow, where a present form refers to the future.

Because the preposition до requires the genitive case.

The noun changes like this:

• школа = school
• до школи = to school

So the ending changes from -а to -и because до always takes the genitive.

Both can be used, but they are slightly different in nuance.

• до школи = to school, toward the school
• в школу = into school, into the school building/institution

In many everyday situations, both are natural and may translate the same way in English. But до focuses more on the destination, while в can emphasize entering.

So йду до школи is a very normal way to say I’m going to school.

You can often omit я in Ukrainian, because the verb form already shows the person.

• я йду = I go
• йду = also means I go, because the ending makes it clear

So both are possible:

• У вересні я йду до школи.
• У вересні йду до школи.

Including я can add clarity, contrast, or emphasis, but it is not always necessary.

No, Ukrainian word order is fairly flexible. The sentence you have is a neutral, natural order:

• У вересні я йду до школи.

It starts with the time expression, which sets the scene: In September...

You could reorder it for emphasis, for example:

• Я йду до школи у вересні.
• До школи я йду у вересні.

These are still understandable, but the emphasis changes. The original version sounds like a normal, neutral statement.