What do you interpret from the ending

Oh, they died, that's what happens when you don't eat. She took them to her „favorite place“, the place from the painting on her wall that Fred compliments when he comes to her house for the first time. It's an imaginary place, it's her idea of heaven. My guess is it's because it's the only place where her mother (the "Beloved Mother" that she was praying to) loves her instead of treating her like shit for being "overweight", as she probably did when the teacher was young. What better way to deal with the trauma than deify your mother, pretend she had a higher purpose, pretend you're saving the world, spread her cause and save a few more young souls along the way, right? I'm being sarcastic, ofc.

The only "enlightenment" the kids could stumble upon would be the realization that the teacher is out of her mind and they were gullible enough to let her drag them towards/to their death. Except the movie makes clear that this is not what happened. The kids actually knew (even if at subconscious level) that the destination is death much earlier, but it's what they "wanted" and what they were pursuing (along with the sense of community and being "loved" and accepted). These kids were all depressed and suicidal (some more some less) to begin with, the teacher "just" brought them closer to the idea and to the point of acting on it, by providing them with a "higher reason", a false one, an excuse.

This is clear from the scene when they gather in her apartment, when she declares them to be accepted as members of the Zero Club. She literally says: "You have been chosen to follow the great path that leads us from our transitory existence to eternal life". Then she congratulates them and they smile and hug and congratulate each other, making it clear, for us, that they accept the outcome.