Amir was from a poor village background, forced into it by Butt and Majid, who took advantage of his inexperience and innocence. At least some slack should be cut for him.
All these come into account, and oh wait, one thing what makes me excuse Aamir and reduce his punishment is that he was forced to bowl a no ball. If you are such an youngster and if you do not listen to what your senior says, you cannot getaway easily, and you may not get into playing XI from next game.
Just one thing, if your senior asks you to skip class, you need to do it. And once you get caught outside wandering to a lecturer, you will not say that your senior has forced you to do so. But if you get caught with your senior, action will not be against you- it'll be completely against your senior, unless you commit something extraordinarily wrong (Do not call bowling a deliberate no ball a "extraordinary" crime, because when doing that to keep the batsmen away from reaching century/reaching to their personal records, this ain't an "extraordinary" one). And for skipping a class, you will be punished by marking absent, which is the punishment to be given to Amir.
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And in my opinion, he should be get a green signal by 2013 August, so that he gets some fair amount of punishment and also enough time to prepare for the WC.