Language / What is Szkole used for?? [8]

I am a beginner in learning Polish.. confused in how the words change when used in sentences. (grammar)

Szkola - School
Szkoly - Schools

What is Szkole used for?

For 'how is school? ' can we just say 'jak jest szkola?' or 'jak jest szkole'?
why 'szkole'?

Any quick guide on Polish grammar would be useful too..

Thanks,
Krish