If you want to do graduate studies at same school you did your undergraduate do you have to reapply to gradute school or will they automatically accept you?

Answer 1

yes. Your undergrad application is independent from your grad school application. So logistically, even you apply the same school where you did your undergrad there, you still have apply again.

The advantage of applying same school is that you might already knew some of the professors and staffs in that school or department because professors usually teach at both undergrad and grad program. If your performance was impressive enough and those faculties and admission counselors think you are a great candidate for their grad program, it might be easier to get in the same school.

It is just like applying a job where the company was the company you previously worked for. You still need to apply and submit your resume again, but just the chances for you to get in is higher if your previous performance was good.