Does the Middle School not want parental assistance... or is it the kids?

I was a very active mom when my son was in elementary school at Cleveland Elementary school. I was the homeroom mom numerous times, always join the PTA, participated in every First Friday and duty free lunch. I bring in extra stuff accomodating the wish lists of even more than my kid's teachers'. I donate can tops, recycle cans to help raise money for the gym, turn in my box tops, plant the promise of drug free bulbs, volunteer to chaperone field trips, donate books to the library, etc. But... now my son has graduated to middle school. I had heard rumors that the middle school simply did not very want parents to come in, help out, etc. But, as I enrolled my son, and went to the orientation,.. the school officials all said that they had heard this too but that it simply was not true. They assured the community that they wanted all the help they can get, to come in anytime, to volunteer. But, I can hardly get in there to give my kid a Tylenol. It seems to be a limited to 'the office and thats it' deal. Is it maybe the kids and not the staff? Maybe it's the age or stage or something but... my usually loving child does not even look back at the Jeep before rushing off to first block now. How are you doing with your middle schooler?