Do you think class rooms should be separated between smokers and non smokers if there are enough students of each type to make it work?

Not at all. Smokers can take it outside during breaks. Non-smokers shouldn't be exposed to other people's unhealthy habits.

When I joined the service in basic training we had to stand in formation with smokers (butt suckers) allowed to smoke and we could not leave.

Their inconvenience about going outside away from the building does not bother me at the least. (I always hope it rains on them also.

No. It is a military bad practice. Smokers are notorious for breaking discipline in training ambush or on patrol. I had to have SNCO's and NCO's search for cigarettes prior to sending out patrols, listening posts, and observation posts. Spend enough time in the field and you can smell a smoker from a long way, ambushes and patrols blown again. It is legal so I couldn't stop them from smoking on their own time, (before morning quarters and after secure) but it got you and your chain of command up to and including me, a Saturday 25 miler step off at 1900, if you did it on my time, garrison or field.