Responsible owners of any breed DO take care not to put their dogs into situations where harm could occur, either to the dog or to other humans. Even though my rottie, Max, is a wonderfully happy, even-tempered dog, I don't take him to my school several times a year as I do with Ben, my saint.
Do I think that Max would bite or lunge at a student? No..... I simply don't want to take the risk that some unforseen circumstance would frighten him or frighten a child and give either a bad experience. I am responsible for his well-being, so I must be careful to do what it best for him. It is a matter of knowing your dog (no matter the breed) and using sound judgement!