My DS6 writes backwards all the time. I gave him a hand held mirror that he carries around with him so he can write secret messages in his notebook to his friends and then they use the mirror to read it. I asked the teacher about it and she said, "Isn't it wonderful! We learned all about Leonardo Da Vinci in class and Leonardo wrote backwards in many of his journals." She let my DS share his notebook and mirror at Show and Tell and it was a huge hit. So, it seems like you have little Leos on your hands!