How dangerous is it for teens to text and drive?

Very Dangerous. Just like it is for everyone else. Statistics from AAA (I believe) have shown that every 2 seconds your eyes are off the road your chance for a crash doubles (4 seconds x4, 6 seconds x8, 8 seconds x16, etc).

Texting is possibly more dangerous for teens because they generally lack the driving experience that adults have. This means that if a text message causes an experienced driver to make a small mistake, they may be able to correct for that elsewhere. If an inexperienced driver makes a mistake because of a text message, they may not be able to make up for it.