I don't believe students lower than 4th year should be practicing on patients outside of a veterinary school (where clients might understand that a student will probably be involved in their pet's care to some extent). The veterinary school's sole purpose is to teach students paying $40K+ a year the best way to complete proceedures. Clients should most certainly know if non fully-trained students will be practicing on their pet. I would most certainly want to know if a student of ANY year would be involved in proceedures on my pet!