Learn Hardcore Spanish (Spain): No es que el partido fuera aburrido, es que yo pensaba en el examen de biología. - It’s not that the match was boring, it’s that I was thinking about the biology exam.

fuera is the imperfect subjunctive of ser.
Saying No es que el partido fuera aburrido is a set pattern that means something like:
- “It’s not that the match was boring (in itself)…”

If you said:

No es que el partido fue aburrido – This sounds wrong to a native; the indicative breaks the pattern.
No es que el partido era aburrido – Same issue; no es que calls for the subjunctive here.

So the structure is:

No es que + subjunctive = “It’s not that …” (denying or playing down a possible explanation).

More generally, why is the subjunctive used with No es que?

With no es que, the speaker is not simply describing reality, but commenting on or rejecting an explanation, opinion, or interpretation.

Es que el partido es aburrido – “The thing is that the match is boring” (straight statement, indicative).
No es que el partido fuera aburrido – “It’s not that the match was boring” (you’re rejecting that idea; hence subjunctive).

The subjunctive appears because:

The clause after no es que is treated as a hypothesis / interpretation, not as a fact the speaker is asserting.
The negation (no) reinforces that you’re distancing yourself from that content: “I’m not saying that X (even as a hypothetical) is the true explanation.”

So: no es que + subjunctive, almost formulaic, whenever you want to say “It’s not that X…, it’s that Y…”.

What does the whole No es que …, es que … structure do in this sentence?

It contrasts a rejected explanation with the real explanation.

In this example:

No es que el partido fuera aburrido
→ The speaker denies or downplays “the match was boring” as the reason.
es que yo pensaba en el examen de biología
→ The speaker gives the true reason: “I was thinking about the biology exam.”

Functionally:

It softens or corrects an impression: “Look, I’m not saying the match was boring…”
Then it gives a more accurate explanation: “…the thing is, I had the exam on my mind.”

This pattern is very common in spoken Spanish:

No es que no quiera ayudarte, es que ahora no tengo tiempo.
No es que sea caro, es que no me compensa.

What is the role of es que in the second part es que yo pensaba en el examen de biología? Could you just say yo pensaba en el examen de biología?

es que here is a very common discourse marker that roughly corresponds to:

“it’s that…”
“the thing is…”
“what happens is that…”

So:

es que yo pensaba en el examen de biología
≈ “it’s that I was thinking about the biology exam” / “the thing is, I was thinking about…”

You can drop es que and say:

Yo pensaba en el examen de biología.

That’s grammatically correct, but es que:

Makes it feel more explanatory and conversational.
Explicitly marks this as the reason for something that was just mentioned or implied (e.g. “why I didn’t enjoy the match so much / why I seemed distracted”).

In everyday speech, Spaniards use es que constantly when giving reasons or justifying something.

Why is it pensaba and not pensé or something like estaba pensando?

pensaba is the imperfect form of pensar, and it’s the natural choice here because it describes:

an ongoing, background mental state during the match, not a single completed thought.

Nuance:

yo pensaba en el examen – “I was (kept / used to be) thinking about the exam” (durative, background).
yo pensé en el examen – “I thought about the exam (at some point)” (a more bounded, completed event).
yo estaba pensando en el examen – Also works, similar meaning, but slightly more vivid/progressive, like “I was (right then) in the middle of thinking about it.”

In this context, pensaba fits the idea of being mentally elsewhere throughout the match, which explains why the game didn’t feel boring but the speaker wasn’t engaged.

Why is it pensaba en el examen and not pensaba sobre el examen?

With pensar, Spanish typically uses:

pensar en + thing/person – thinking of / about something in general.

Examples:

Pienso en ti. – “I think of you.”
Estaba pensando en mi futuro. – “I was thinking about my future.”

pensar sobre does exist, but it’s:

Much less common.
Typically used for “thinking about a topic” in a more analytic or reflective way, like “reflect on / think about (an issue)”:
- Estoy pensando sobre el problema de la pobreza.

In everyday speech, when you mean “my mind was on X”, you use pensar en:

Yo pensaba en el examen de biología = “My mind was on the biology exam.”

Why is it el partido and not el juego for “game / match”?

In Spain:

el partido is the default word for a sports match (football, tennis, basketball, etc.).
el juego is more like “game” in a very general sense (a children’s game, a board game, the concept of play, etc.).

So:

el partido de fútbol/baloncesto/tenis – “the match / game (of football, basketball, tennis)”.

Using el juego for a sports match would sound odd to a Spaniard in this context.

(You will see juego in some Latin American contexts for sports, but partido is still very standard for matches; for Spain specifically, partido is clearly the right choice here.)

Why do we say el examen de biología with the article el? Could you say just examen de biología?

In this context, el examen de biología is a specific exam the speaker assumes you know about (for example, the biology exam they have tomorrow).

Spanish normally uses a definite article (el / la / los / las) where English often omits it.

Compare:

Tengo examen de biología. – This is also possible and sounds a bit more generic or informal, like “I have a biology exam (coming up).”
Tengo el examen de biología. – More specific: “I have the biology exam (we’ve been talking about / on a specific date).”

In the original sentence, el examen de biología sounds natural because it’s probably referring to that particular upcoming exam already known in the context.

Is there a reason for the explicit yo in es que yo pensaba en el examen de biología? Could we drop it?

You can absolutely drop yo:

es que pensaba en el examen de biología.

Both are grammatically correct. The explicit yo adds emphasis on the subject:

It subtly contrasts me with something/someone else, or
Highlights that we’re talking about my mental state.

This is often used when:

Answering a question like “Why were you so quiet?” → Es que yo pensaba…
Contrasting with another person: Ellos estaban muy atentos, pero es que yo pensaba en el examen.

So yo is optional but gives a small emphasis: “I was the one thinking about the exam.”

Could you say No es que el partido hubiera sido aburrido instead of fuera aburrido? What’s the difference?

Yes, you can say:

No es que el partido hubiera sido aburrido, es que yo pensaba en el examen de biología.

hubiera sido = past perfect subjunctive (pluperfect subjunctive). Nuance:

fuera aburrido – Describes the match as a general past state; very natural and common.
hubiera sido aburrido – Feels a bit more distant or hypothetical, often used when you’re talking about a completed situation in the past in a more “theoretical” way.

In everyday spoken Spanish, with this kind of justification, fuera aburrido is more straightforward and idiomatic. hubiera sido is not wrong, just a bit heavier and less colloquial for this context.

Is this sentence more formal or informal? Would people in Spain actually say it like this?

It’s perfectly natural, colloquial Spanish. Spaniards really do talk like this.

No es que … es que … is extremely common in everyday speech when explaining or justifying something.
The tenses and vocabulary (el partido, pensaba en, examen de biología) are neutral – neither slangy nor particularly formal.

You might hear variations like:

No es que el partido fuera aburrido, es que estaba pensando en el examen de biología.
No es que el partido estuviera aburrido, es que tenía el examen de biología en la cabeza.

But the original sentence is completely idiomatic Iberian Spanish.