1. I am at school.
2. She is from Spain.
3. We are in the garden.
4. You are a bad boy.
5. The mouse is grey(а не gray).
6. He is 20 years old.
7. I am a teacher.
8. He is at home.
Это формы Present Simple глагола (to) be. Когда стоит I, нужно ставить am, когда we, you, they - are, когда he, she, it - is.