Be careful!

For negatives add 'n't' or ‘not’.
I wasn’t late for school this morning.
I was not late for school this morning.
She wasn’t with her friends last Saturday.
She was not with her friends last Saturday.
We weren’t tired yesterday.
We were not tired yesterday.

We say... We don’t say...

Were you late for school today? Yes, I was. (NOT You were late for school today? Yes I was.)
Was she with her friends last Saturday? No, she wasn’t. (NOT She was with her friends last Saturday? No, she wasn’t.)
Was he tired yesterday? Yes, he was. (NOT He was tired yesterday? Yes, he was.)
(For a normal question we use was + pronoun. To show surprise you can use pronoun + was.)