charges waiting until adult?

What is the name of your state?
iowa

My son was going to be charged with harrassment in January. I recevied a letter stating that they were not going to charge him at this time, but when he turns 18 in June, they will reopen the case and press charges then. His ex-girlfriend wants to drop the charges, but was told it wasn't up to her anymore????
He has been arrested twice as a juvenile - once for simple assault and once for 3rd degree criminal mishieve. I'm assuming that is probably why they are waiting to charge him.
Is it worth it to hire a lawyer or is this common practice??

Yes, it is worth hiring an attorney.

Although the prosecuter is allowed to either file now or wait, since the offense was committed while your son was a juvenile, the juvenile court has jurisdiction unless they specifically waive jurisdiction to a higher court.

Get him an attorney then kick his butt for being stupid.