Dental Assistant with medical cannabis card? ?

I live in California. I've been a legal cannabis card holder all through my schooling to become a dental assistant. I am suppose to be drug tested some time around internship this month. I haven't smoked in 2 months because of this. But I'm wondering if they can really turn me away if I did have it in my system since I am a legal card holder. It's not like I'd go to work high or anything like that. I am a straight A student and very responsible. I've held a job for 4yrs straight with no write ups or problems at all. So can dental assistants be medical cannabis patients in the state of ca? Or can they turn you away for the medication in your system? I cannot find any information about this, but the private school I attended was strict on this subject. If you were tested with weed in your system and you didnt have a legal card, you were expelled. If you were tested and had a legal card, you were suspended until it was out of your system. I don't know if this is just the school's rules or if you really cannot be a dental assistant and be a medical cannabis patient. Any one with legit information or references would be very much appreciated!!!