Question

John or Mary (is/were/are) at school

Answer 1

John or Mary are at school (present)

John or Mary were at school (past

Step-by-step explanation:

SO if it you are speaking about the past you use were and if you are speaking about the present you use are.

Answer 2

were or are

Step-by-step explanation:

if talking about the past use "were" if talking about the present use "are"