El problema avergonzó al alumno.

Because this sentence uses the personal a.

In Spanish, when the direct object is a specific person, animal, or personified being, you normally put a before it. Since el alumno is a specific person, it becomes:

• a el alumno → al alumno

So al here is just the contraction of a + el.

Compare:

• Veo la mesa = I see the table
• Veo al alumno = I see the student

The a does not mean to here. It is just the marker for a personal direct object.

The verb form tells you.

Avergonzó is third person singular, so the subject must be singular. Both el problema and el alumno are singular, but al alumno has the personal a, which strongly signals that it is the object, not the subject.

So the structure is:

• El problema = subject
• avergonzó = verb
• al alumno = direct object

In other words:

• The problem embarrassed the student

This is a very common pattern in Spanish, even if English learners sometimes expect the person to be the subject.

It is the preterite tense, third person singular, of avergonzar.

So:

• yo avergoncé
• tú avergonzaste
• él/ella/usted avergonzó

The preterite is usually used for a completed action or a single event in the past.

So El problema avergonzó al alumno suggests that the embarrassing happened as a completed event.

The accent mark shows both pronunciation and meaning.

• avergonzo = I embarrass / I do embarrass
• avergonzó = he/she/it embarrassed

That written accent helps distinguish the present-tense yo form from the preterite él/ella/usted form.

So the accent is important: it tells you this is a past tense form.

The difference is mainly one of aspect:

• avergonzó = preterite, a completed event
• avergonzaba = imperfect, background, repeated, ongoing, or descriptive past

So:

• El problema avergonzó al alumno = The problem embarrassed the student.
  This sounds like a specific event or completed reaction.

• El problema avergonzaba al alumno = The problem was embarrassing the student / used to embarrass the student.
  This sounds more ongoing, habitual, or descriptive.

Yes, both exist, but they mean different things.

• avergonzar a alguien = to embarrass someone
• avergonzarse = to feel ashamed / to become ashamed

In your sentence:

• El problema avergonzó al alumno = The problem embarrassed the student

If you used the reflexive:

• El alumno se avergonzó = The student became ashamed / felt ashamed

So the non-reflexive verb focuses on what caused the feeling, while the reflexive focuses more on the person experiencing shame.

Alumno is a masculine noun, so it naturally takes el.

There is a separate rule where some feminine singular nouns beginning with stressed a- take el in the singular, such as:

• el agua
• el águila

But that rule does not apply here, because alumno is already masculine.

So:

• el alumno = the male student / the student (masculine)
• la alumna = the female student

Yes. Spanish word order is more flexible than English.

The neutral order here is:

• El problema avergonzó al alumno.

But you could also say:

• Al alumno lo avergonzó el problema.

This version puts al alumno first for emphasis or contrast. The extra lo is a common resumptive pronoun.

Both mean essentially the same thing, but the second sounds more marked or emphatic.

Yes. Alumno and estudiante can both mean student, but they are not always used in exactly the same way.

• alumno often emphasizes someone as a pupil in relation to a school, class, or teacher
• estudiante is more general and can mean a student in a broader sense

In many contexts, either one works well.

In standard Peninsular Spanish, it is approximately:

• a-ber-gon-THO

A few useful points:

• v and b sound very similar in Spanish
• z in Spain is pronounced like th in think
• the final ó syllable is stressed: avergonzÓ

So avergonzó has the stress on the last syllable.

Yes.

The standard direct-object pronoun would normally be:

• El problema lo avergonzó. = The problem embarrassed him.

If the student is female:

• El problema la avergonzó.

In parts of Spain, you may also hear le for a masculine singular person:

• El problema le avergonzó.

That is related to leísmo, which is common in Spain. But if you are learning standard grammar, lo is the usual direct-object pronoun for a male person here.

Yes, al can mean to the, because it is literally a + el.

For example:

• Voy al colegio = I’m going to the school

But in your sentence, al is not showing direction. It appears because of the personal a before a human direct object:

• avergonzó al alumno

So you should not translate it literally as embarrassed to the student. Here it simply marks the student as the personal direct object.

Yes. Spanish often uses constructions where the thing causing the emotion is the subject, and the person feeling it is the object.

So this pattern is very natural:

• El problema avergonzó al alumno.
• La noticia sorprendió a Marta.
• La película emocionó a Juan.

This can feel different from some English habits, but it is completely normal Spanish.