"It is a school."
Translation:To jest szkoła.
Note that it makes more sense as a short answer (- Co to jest? - To szkoła.) than as a standalone sentence.
Because the word "to" works here like a demonstrative pronoun (and mind you, the word "to" has also many other functions). So, the phrase is an example of the simplest demonstration.
- To jest szkoła - [This is a school / It is a school]
- To jest mój kot - [This is my cat / It is my cat]
- To jest jabłko - [This is an apple / It is an apple ]