Dear E.,
You are very smart to be nervous, but make up your mind that you will stay in touch - that is communicative with your son and stay in communication = close - with his teachers and then you can get some sleep. Just make it one of the things that you plan into your day and week. No one told me that my beloved son would go crazy and get out of hand and be snotty and oh, I don't know what else, it has been a long time now. But I do remember the pain, and wish that someone had warned me - they change.
And, they change not only internally and sexually and that sort of thing, but their peers become so powerful and so important to them. Just be certain that he knows how important he is to you and his Dad, and keep the warm comradely - not fussy and worried - communication going. ....And 'never give up' - that is what Winston Churchill said - in a speech at a College in the United States , I think it was during or after WW11. Anyway, it is still great advice.
This is the time when he will start thinking about what He likes to do, what he is interested in and his own value system. He also will be noticing the value system of his peers - um, hum, Yikes.
Good Luck, C. N.