It's interesting to read how things vary - and yet are the same.
My Bar Mitzvah story was very strange - I was actually living in Israel at the time and was the youngest in my class. So it was very annoying when in 7th grade many of my friends would vanish for Bar Mitzvah class (taught by a really nice guy we called Rabbi Yossi who taught in his dining room). Rather than being bored at home I started just tagging along. This went on for several months.
One day my dad brought up that it was close to time for us to arrange for Bar Mitzvah classes. He was floored when I told him I'd already been going for months.
I ended up having a very traditional service (lots of Torah reading, but no speech

), and pissing off some of the congregants because I insisted on giving some of the most prestigious Aliyot to my friends who had been Bar Mitzvahed just weeks before (but my dad backed me up on that).
Then a nice but casual party at home (all of which got paid for out of the gifts I received - we weren't exactly flush at the time).
Later I got in trouble for being very slow to write thank you letters (I mean, it's not as if I got to keep any of the money

).
Still - good memories....