our classes last an hour as well, but our puppyclasses isn't obidienceclasses, but we do introduce the pups to different things each time, sit, stay, retrieving, tracklaying, walking in/without leash etc. etc., but most of the time we spend on socialising and playtime. When they get older 6 month we have obidience classes.
We never recommend collars with chains or half chains to pups. When they start on obidienceclasses we talk about it if necesarry. Usually only one or two dogs are adviced to use the collar but the owners are carefully instructed on how to use it.