Ang mag-aaral ay nakaupo sa silid-aralan habang binabasa ng guro ang bagong aralin.

Ay marks a topic-comment structure. In this sentence, Ang mag-aaral is presented first as the topic, and ay nakaupo sa silid-aralan... is the comment about that topic.

So:

• Ang mag-aaral ay nakaupo... = The student is sitting...

This is correct and fairly neutral, but it can sound a bit more formal or written. In everyday speech, many speakers would more naturally say:

• Nakaupo ang mag-aaral sa silid-aralan...

Both mean the same thing.

Yes, mag-aaral can mean either:

• student / learner as a noun
• will study as a verb form

The meaning depends on context.

Here, it means student because it is part of the noun phrase Ang mag-aaral, and that noun phrase is followed by ay nakaupo. So the sentence structure tells you that mag-aaral is a person, not an action.

Compare:

• Ang mag-aaral ay nakaupo.
  = The student is seated.

• Mag-aaral ako mamaya.
  = I will study later.

Nakaupo describes a state: being seated or sitting down in a seated position.

So in many contexts, nakaupo is the natural way to say:

• is sitting
• is seated

By contrast, umuupo usually refers more to the action of sitting down or to the act/habit of taking a seat, depending on context.

So:

• nakaupo = already seated
• umuupo = sitting down / taking a seat / sits

In this sentence, the student is already in that position, so nakaupo fits best.

Sa silid-aralan means in the classroom or at the classroom, depending on context.

• sa = a location marker, often translated as in, at, to, or on
• silid-aralan = classroom

So:

• nakaupo sa silid-aralan = sitting in the classroom

A useful thing to remember is that sa is very common for places and directions.

Habang means while or as. It connects two actions that happen at the same time.

Here it links:

• Ang mag-aaral ay nakaupo sa silid-aralan
• binabasa ng guro ang bagong aralin

So the meaning is:

• The student is sitting in the classroom while the teacher is reading the new lesson.

It introduces a subordinate clause, similar to English while.

This is about focus/voice.

Binabasa is a patient-focus form. That means the thing being read is the ang-marked noun:

• ang bagong aralin = the new lesson

So:

• binabasa ng guro ang bagong aralin literally works like
  the new lesson is being read by the teacher

In natural English, we usually translate it actively:

• the teacher is reading the new lesson

If the sentence used nagbabasa ang guro, then ang guro would be the focused noun instead. Filipino often chooses the verb form based on which noun is marked with ang.

Because the verb binabasa is in patient focus, the doer of the action is marked by ng.

So in:

• binabasa ng guro ang bagong aralin

the roles are:

• ng guro = the teacher, the one doing the reading
• ang bagong aralin = the lesson, the thing being read

This can feel backwards to English speakers at first, because English usually centers the doer as the subject. In Filipino, the marking depends heavily on the verb focus.

Because Filipino uses a linker between a modifier and the word it modifies.

Here:

• bago = new
• aralin = lesson

Since bago ends in a vowel, it takes the linker -ng:

• bagong aralin = new lesson

This linker is very common in Filipino.

Examples:

• magandang araw = good day
• malaking bahay = big house
• bagong libro = new book

Yes, because they belong to different clauses.

In the main clause:

• Ang mag-aaral ay nakaupo sa silid-aralan

the ang phrase is Ang mag-aaral.

In the clause introduced by habang:

• binabasa ng guro ang bagong aralin

the ang phrase is ang bagong aralin.

So this is not a problem. Each clause can have its own focused/topic noun.

Not exactly.

Ang is often translated as the, but its main job is not simply to mark definiteness. It usually marks the focused/topic noun of the clause.

So sometimes ang may look like the in translation, but grammatically it is doing something different from the English article.

For example:

• ang mag-aaral
• ang bagong aralin

Both are naturally translated with the here, but ang is really part of the Filipino noun-marking system, not just a direct equivalent of English the.

Yes. Filipino word order is flexible, especially when the markers already show each noun’s role.

A very common alternative is:

• Nakaupo ang mag-aaral sa silid-aralan habang binabasa ng guro ang bagong aralin.

This means the same thing.

The version with ay is more of a topic-first structure, while the version without ay is often more natural in everyday conversation.

The hyphens reflect standard Filipino spelling in certain derived or compound forms.

• mag-aaral is a conventional spelling and helps show the structure of the word clearly.
• silid-aralan is a compound form meaning classroom.

For a learner, the important thing is to recognize them as single vocabulary items:

• mag-aaral = student
• silid-aralan = classroom

You do not need to analyze the hyphens every time you read them, but it is good to know that they are normal and meaningful parts of the spelling.