Then I received a call from Sylvan Learning telling me that my son's reading comprehension is between second and fifth grade! What should I do? Perhaps you can tell me how to motivate a teenage boy to read and read with comprehension. This is so crucial because of the PSAT's. Please let me know what to do in this situation.
I believe your son needs testing, but not a reading test. When grades drop so drastically and behavior changes so much, parents need to rule out drug/alcohol usage through a drug assessment by a professional. Contact the school counselor for a possible free assessment. Don't let your son talk you out of it. Emphasize that it is to "rule out" any drug/alcohol abuse.
As for the girl, you have already experienced a typical teen reaction -- you pushed and forbade and he pushed back. You can and should certainly limit his talking on the phone to anyone and how much he goes out. Sometimes a reverse technique helps. You might try telling him that he can invite his girlfriend over on the weekend for dinner with the family or for a movie at your house (while you are there, of course) when he has done all his homework for the week. You can have him bring home a report from his school to verify this. If she truly is the problem, she either won't come, or she will come and everyone can learn a little more about each other and she will cease to be a negative influence.