Does graduate school qualify for full time student?

You can be a full-time student in graduate school.    If you are looking at education credits available to you in grad school, you cannot use the American Opportunity Credit---that is only for undergrad school.   But you can use the Lifetime Learning Credit or Tuition and Fees.

Or----if you are asking because you need to know if you can claim a dependent child who is in grad school--yes you can if the student is either under the age of 24 or ---if older than 24 the student has an income less than $4300.

We can be more helpful if we know why you are asking if a grad student can be a "full-time student" but the short answer is yes.