Translation:There is a small kindergarten teacher on the curtain.
OK, so after flying and walking on water, now the poor creature is on the curtain. What's next?
I think it is because in this example, the curtain is kind or the subject. Whereas in your example the teacher is the subject. I'm not hungarian but finnish, and our languages work similarily in this regard: "Verhossa on opettaja" = "There is a teacher on the curtain" "Opettaja on verhossa" = "A teacher is on the curtain"
I also ran into this problem. Although now I think it's because it's unnatural for English to start a sentence like that, with a newly introduced subject (and it's newly introduced as the "a little..." indicates). In these cases it's way more natural (and generally grammatically correct, I guess) to use the existential phrase "There is a...".