My 5 month Min. Schnauzer bit our obedience instructor when she touched his feet. Should I be concerned?

My almost 5 month old miniature schnauzer puppy has been in puppy obedience class for 3 weeks. She is doing very well with her commands (sit, down, come) and up until this past Saturday has interacted well with all the other handlers and dogs in the class. However, at our last class, she growled at and bit the training instructor when she touched her feet. The bite did not break the skin or leave any red marks. I was very surprised by her reaction since she has never before displayed any behavior like this. She has been to the groomer once so far and was nothing other than a wiggly puppy. I have her on the table weekly for beard cleaning and brushing and nail trimming every two weeks and no problem. The previous week she was held and handled by all the other dog owners without incident. We have now been expelled from class and referred to a certified dog counselor with whom we have an appointment.

My gut feel is this is was a one-time-incident possibly spurred by any one of the following conditions:
- The instructor is a very, very, very large lady (Ellie did growl the first time she saw her).
- All the other puppies in the class are BIG (great dane, german shepard, doberman)
- All the other handlers had assistants or other family members with them (my husband was not able to attend this time - first time I was alone)
- Just as Ellie was dwarfed by the size of the other puppies, I'm a small person myself.
- I had stepped away from Ellie preparing to do a recall when the instructor approached and touched her. Her attention was focused on me.



I have talked with the breeder and the owner of Ellie?s father and they assure me none of the dogs they have ever bred have been aggressive ? both
are very reputable breeders. I have a 4 year old MS (from the same breeder) that I have raised and obedience trained. He is Canine Good
Citizen ? so, I?m not wet behind the ears in this regard.



Should I be concerned?
Lin