This song is about wanting to rebel, but not realizing the cost of your defiance.  "I've had these jeans since I was born.  And now they're ripped. And now they're torn."  The metaphor is obvious.  "Jeans" sounds a lot like "genes", doesn't it?    The jeans represent things that have been handed down to you by your parents and/or society.  The destruction of the jeans symbolizes several things: the speaker's view of his parent's traits, the start of his rebellion, a bastardization of innocence.

"All my friends have skateboards.  I want the toys of other boys.  I want a knife and a gun and things but Mom and Dad will not give in."  Fairly self-explanatory.  There are several reasons for his desire to rebel: a want to be 'cool', a want to covet, a want to feel powerful and 'grown up'.  But none of these things can be provided through what society has given him.

"I can't put the needle in." While Thom insists that this is not a drug reference, there is no doubt that it is a negative image.  It could be to "take blood", i.e. "take a piece of your soul".  The speaker will become all the things he wants to be, but at a great price.

The second verse is basically Thom's acknowledgement of the poison he has taken.  And while he realizes his mistake, he cannot bring himself to correct it, and even enters a state of denial, first stating, "I know just what it is", but then, "Too scared to know the reason why."  The final tragedy comes in the last line: "All my friends say bye bye."  Thom cannot bring himself to destroy himself, and is rejected.