The school administration is within their rights, as a private institution, to require that all employees must not drink or smoke. It’s their prerogative. When you sign the contract you are agreeing to uphold these rules and regulation. No one holds a gun to your head. You either abide by the rules, or seek employment elsewhere.
She didn’t know she was pregnant?
Your questions is irrelevant. What we do know is that the woman was terminated for a violation. Until we understand both sides of the story we should refrain from automatically assuming that the school was wrong to terminate this teacher.
She got married 3 weeks after she got pregnant. She may not have even realized she was late at that point. Being stressed can impact your schedule also.
Some people don’t feel pregnant until about 8 weeks.