Translation:This perfect child is in a perfect school.
I think in English 'ideal' and 'perfect' are similar but not exactly the same, at least in that there are contexts where interchanging them would sound weird. Duolingo is accepting "idealne" as either "ideal" or "perfect." Is there a distinction?
There's also "perfekcyjne" for "perfect", but "idealne" seems better in the Polish sentence and "perfect" in the English one.
Does it also mean "ideal" as in a "perfect imaginary model that does not exist in reality"? That phrase would be perfect to complain that some example is just not for the real world.
No. It means that something is perfect but not imaginary. There is also „ideowy” meaning ideological. To render it we would probably go with: „modelowy”, „wzorcowy”, „koncepcyjny”, „odniesienia/referencyjny”.