Depending on the school district, it could be any sort of test. Some of the districts here where I live use hair testing, and some use urine. I don't know of any that use blood or saliva testing. On the ones that take urine tests, no one watches you urinate. No one here has any way of knowing what type of test you will face or predicting the future for you. I'm surprised you didn't think about this before applying for and entering that professional field. Here in Texas where I live, they routinely randomly test teachers for drugs even after the initial drug screens. And the ones that don't pass don't keep their jobs.