I'm really impressed by how much a kid can learn. I probably was kind of the same, but today, all these kids, they play with computers and they know how to count, spell, read and write before to start serious schooling! (before 6 years of age) This isn't specific to my kid and that's why I'm saying: these kids.
Here is a page by Calvin who wrote the alphabet! He's 58 months old (i.e. 5 years old in 2 months). He has known his alphabet for over a year already.