Learn Farsi: مدرسه سمت چپ است. - The school is on the left side.

While be samt-e means "towards" (indicating movement), this sentence describes a fixed location. When talking about where something is rather than where it is going, Farsi often drops the preposition به (be). So, سمت چپ (samt-e chap) simply means "on the left side."

Is there a hidden connector vowel between سمت and چپ?

Yes, there is an invisible ezāfe connecting them, so the phrase is pronounced samt-e chap. The ezāfe links the noun سمت (samt, side) to the adjective چپ (chap, left) to form "the left side."

Could I use طرف (taraf) instead of سمت (samt) in this sentence?

Yes! You can absolutely say مدرسه طرف چپ است (madrese taraf-e chap ast). Both سمت (samt) and طرف (taraf) mean "side" or "direction" and are perfectly interchangeable here.

Why isn't there a Farsi word for "on" like in the English translation?

In English, we say something is "on" the left. In Farsi, you do not need a spatial preposition like روی (ru-ye, on) for these directions. Just stating the side with () naturally translates to "on the left side."