No, it is not an official manner to write "9," and pupils in elementary school are not instructed to do so. However, many adults would prefer to write "9" in this manner, and it is a mark of maturity to write (or draw) "9" in this manner. This custom may have originated as a joke or sign of the zodiac. In fact, writing "9" backward is used by some artists as a statement that they are unoriginal. Others use it as a protest against society. Still others use it as a joke. Some say they write "9" backward because it's easier to read when written that way. There is no real reason why someone would write "9" backward except as a statement that they are being ironic or are a mature artist/writer who knows what they are doing.