Learn Icelandic: Skólinn er til vinstri. - The school is to the left.

In Icelandic, the word for 'the' attaches to the end of the noun. The base word for 'school' is the masculine noun skóli. To say 'the school', you add the definite article suffix -nn, making it skólinn.

The preposition til usually makes the next word take the genitive case. Why doesn't vinstri change?

You are right that til normally triggers the genitive (possessive) case. However, the directional words for left (vinstri) and right (hægri) are special exceptions. They never change their endings, regardless of what preposition comes before them.

If til vinstri means 'to the left', how do I say 'to the right'?

You just use the same pattern and swap the direction word. The Icelandic word for 'right' is hægri, so you would say til hægri.

Could I use the phrase vinstra megin instead of til vinstri here?

Yes, you could say Skólinn er vinstra megin, which translates to 'The school is on the left side.' While til vinstri literally means 'to the left', both phrases are very common and often mean the exact same thing when describing where something is located.