I just today, went and spoke to our locat obediance school (all these posts are kinding scaring me LOL
) Anyway she said NO chock collar at all! especially for a yorkie. I don't know if your town will be different but I asked too because when I took our bulldog for classes they said I should get one for him...I couldn't though (no neck LOL)
Hopes that helps. (I know each place can have different feelings about suck things, but this lady was ADAMANT that there was NO chock collars)