I agree with CheekyChops, Colleges need punters and staying the course is more important than signing up or coming over all enthusiastic at the interview. Get him to ask lots of questions; what will the timetable be like, how much homework will I get, what units are in the course etc. Lots of our students sign up without realising that they will be surrounded by only boys! And 17 year old boys sometimes would prefer girls in their classroom! If he signs and then drops out, he has wasted a year and the College loses money, as well as getting another "drop out" statistic, which is not really fair on the college or its teachers.
So, make sure he is doing the course he wants, and can commit to it for 2 years.