Learn Russian: Школа далеко, а магазин близко. - The school is far, and the shop is close.

In Russian, the verb "to be" is almost always left out in the present tense. Instead of saying "The school is far," you literally just say Школа далеко (School far).

Why does this sentence use а for "and" instead of и?

In Russian, и is used to simply add things together. The word а is used when you are contrasting or comparing two things. Since this sentence contrasts the distance of the school (far) with the distance of the shop (close), you use а. It translates to "and" here, but it works a bit like "whereas" or "on the other hand".

Why don't далеко and близко change endings to match the gender of the school and the shop?

Because they are adverbs (words that describe where or how something happens), not adjectives. While adjectives change their endings to match the gender of a noun, adverbs like далеко (far) and близко (close) are fixed and never change.

Is the comma before а required?

Yes! A strict rule in Russian punctuation is that you must always put a comma before the contrasting words а (and/whereas) and но (but).