Haha... yeaaaaah... I totally agree. It's not very obvious if you got it right or wrong.
If we had had more time I think I'd have added some sound effect or different images to indicate if the answer was right or wrong.
However, at least at the end of the game the "kids" actually talk about their results, and that also reveals the number of good answers you had... :)
Also the one where the teacher throws the book out of the window, is when you get it right! xD