I think your targeting the wrong audience.

High-school kids are going to be typical kids for 15 to 17 yo. They are punks, insolent, know-it-alls, in my high-school we had up to 60 kids in a class and if someone didn't fall out from drugs/alcohol, and there wasn't a fight, it was considered a good day by the teacher. It is the duty of every kid that age to push the limits and to chafe against all decorum and authority.

That this is a well-off school, with kids coming from well-off families just makes things worse. Think throw-away, latch-key kids who have have been catered to all their lives.

I can't imagine a wild food class has any relevance to them. Likely they took as a way to blow off some time without working at it. If they want food they go home or Mick-Ds. The subject being irrelevant brings on boredom, listlessness, bad behavior. Not interested in wild foods as food they, like most kids that age, want to get high. If you could point out two or three thing they might alter their minds by smoking, eating, or rubbing it into their bellies -not that you would or should- they would have perked up and paid attention. Kids that age need a 'hook'.

These are the same people the summer blockbusters cater to with fiery explosions, shootouts, gratuitous nudity/sex/violence. No matter how good you are getting these kids interested in stuff they consider to be weeds was a lost cause if you didn't toss in a few fiery explosions. A couple of nearly naked female assistants might have helped.

You would have better luck teaching petipoint to Hell's Angels.

I think you're going to have better luck with such a classes if you shoot for teaching younger kids. You need them old enough to be physically and mentally competent but young enough to be curious and impressed by authority figures. High-school is too late. Late elementary school, or what is called middle school, might get you a more receptive audience.

No worry. Teaching a class is itself a learning process. If you keep seeking out the right audience, and keep working on your lesson, it will 'click' one day. Teaching is kind of like stand-up comedy.