Junior wasn't doing so well in Kindergarten. His parents were at their wits' ends, what could they do? Finally, Junior's Dad made him an offer: "Son, if you can get straight A's in kindergarten, your mother and I will get you anything you want." Instantly, Junior's marks improved drastically, and at the end of the year, he did indeed have straigh A's. His father said "Well Junior, you kept your end of the bargain: What is it that you want?" Junior said "Well pop, all I really want is a big sack of 2000 green marbles." Junior's father thought this was getting off pretty light, so he went and bought the marbles.

First grade was the same story though. Terrible marks, and in deparation Junior's parents made him the same offer: If he would get straight A's, the would give him anything he wanted. He again managed to pull off A's. His father asked him "Well Junior, what do you want this year?" Junior said "Well Dad, I really liked those marbles, so if it is okay with you, I'd like 2000 more green marbles." So Junior's father went out and bought him 2000 more green marbles.

In second grade, junior was doing terribly toward the middle of first term, and, as was becoming their standard practive, his parents promised him whatever he wanted, and he got A's. Once again he asked for 2000 green marbles.

And again, and again, and again, the same pattern. third, fourth, fifth, and sixth grades passed in the same way.

By the seventh grade the "If you get A's we'll give you whatever you want" deal had pretty much become a standard thing, and Junior worked dilligently and received A's. When he told his father that he wanted 2000 more green marbles, his father started to get worried. "Son, you could have whatever you want... Wouldn't you rather have a computer, or some new clothes?" "No," said Junior, "all I really want is green marbles." So Junior's father once again got him a sack of 2000 green marbles.

And 8th grade, and 9th grade passed in the same way, but Junior's parents were, understandably, becoming more and more alarmed with each passing year.

In the 10th grade Junior once again asked for 2000 green marbles. "But son," said his father, "you are 16 now! Wouldn't you rather have a car? Or a leather jacket? Or your own apartment?" But Junior said, "No Dad, those things are all great, but what I really like is green marbles." So the next day Junior's Dad bought him 2000 more green marbles, and tried to clear his mind of the whole thing.

Now of course by this time Junio had a lot of marbles. A buttload of marbles. A titanic, glittering, tremendous and amazing pile of green marbles that, to the neighborhood children, appeared to reach up into the sky. By this point Junior, in order to keep his marbles safe (and to increase the available real-estate in his room), had opened a safe-deposit box at a local bank. So Junior took his 2000 new green marbles, and headed off to the bank. He was so excited about his new marbles, that as he hurried across the street to the bank he was hit by a city bus, and immediately killed.

The moral of this story should be obvious: Always look both ways before crossing the street.

This joke is an example of a "Look both ways before crossing the street joke", which is a genre of joke which 12 year olds really seem to like. Basically you tell some long-winded and boring story, which ends with the main character being hit by a bus. Another good example of this type of joke is Monty Python's "Happy Valley" sketch.