Learn Hardcore Japanese: gakkou ha soukisiharai ni gopaasento no waribiki wo kureru sou desu. - I hear the school gives a five-percent discount for early payment.

そうです here expresses hearsay or reported information. It’s like saying “I heard that…” or “apparently…” in English. The speaker is not claiming firsthand knowledge but passing on what they’ve heard.

Why is 学校 marked with は instead of が?

The particle は marks the topic of the sentence—what you’re talking about. By saying 学校は, you’re setting “the school” as the known topic (“as for the school…”). If you used が, you’d be focusing on identifying or emphasizing the subject, which isn’t the goal here.

What does 早期支払いに mean, and why is に used?

早期支払い (sōki-shiharai) literally means “early payment.” The particle に marks the condition or timing—“for early payment” or “when paying early.” It tells us under what circumstance the action (giving a discount) happens.

Why is there の in 五パーセントの割引?

The の links the measure 五パーセント (“five percent”) to the noun 割引 (“discount”), making it a single modifier phrase: “a five-percent discount.” In English you might say “five-percent discount,” and in Japanese you use の to connect the number to the noun.

Why is 割引 followed by を rather than に?

Because 割引 is the direct object of the verb くれる (“give [to me/us]”). The structure is 割引をくれる: “(the school) gives a discount.” The particle を marks 割引 as the thing being given.

What nuance does くれる add here, and why not use あげる or もらう?

くれる indicates that someone gives something to the speaker (or someone in the speaker’s in-group). Here, the school is giving a discount to you (the student). You wouldn’t use あげる because that means “I give (to someone else),” and もらう would emphasize “I receive” (though you could reframe the sentence that way if you want).

Is this sentence polite or casual, and how would you make it more polite?

It’s in the plain (dictionary) form—くれる is plain, and そうです for hearsay is the same in both styles. To make it more polite, you’d use the polite form of the verb:
学校は早期支払いに五パーセントの割引をくれますそうです。
or even
学校は早期支払いに五パーセントの割引をくれるそうですよ。

What exactly does 早期支払い refer to in everyday contexts?

It’s a set phrase combining 早期 (“early period/early stage”) and 支払い (“payment”). In business or tuition contexts, it means “paying by an earlier deadline,” often to incentivize on-time or advance payment. Here it implies “if you pay your school fees early, you get a discount.”