My 1 yr. old Sheltie has been displaying aggression when meeting other dogs. (Snapping and actually trying to fight). I discussed it with my trainer and she stated I should stop the behavior before she has a chance by giving the command "Leave It" and showing her I'm in control of the situation. However, I have been rather unsuccessful. It is getting so bad that I'm afraid to let her come in contact with other dogs. She lunged at my daughter's English Mastiff and accidentally bit my grand-daughter on the arm. I am afraid if this behavior continues, it will become a REAL problem. I don't want to feel as if I can't trust my dog with kids. Any suggestions as to how to stop this behavior would be appreciated.