Consequences of early sexual activity include

One would be teen pregnancy (short story my best friend is 15 and just had a baby girl named Ella 3 days ago, She didn't use any protection and refused to take birth control)

Another one is STD's those are very common especially if you have multiple partners.

A site I'm on says "Becoming less likely to finish High school" I am not sure if that is true. I suppose it could be true if you have a child before graduation but honestly if your education is important to you a child wont stop you from getting it. It may limit you tho. 

Okay I hope this helps! Please rate!