Yes, they can see through your bs, they know what "real sick" looks like and they send you back to class fast if you are annoying.
"The school nurse is someone who doesn't judge, I think I'll go tell her my life story"
"I should be embarrassed that I've been to the school nurse 12 times already this year and it's only October, but that's not stopping me from going to see her again today"
(Bob) Mrs, I feel like I will be throwing up badly
*Throws up intestines*
(School Nurse) Do you want me to call your mom?
(Steve) Mrs I think I am pa-
*Drops to floor*
(Nurse) You look fine to me, go back to class!