Saraaras -
I am impressed with your desire to fight the 10 day suspension. I, personally, think you have a legitimate argument against suspension (if the suspension was, in fact, only for the smoking and not for leaving school grounds to do so).
Based on the rule book, the rules of which you agreed to, you were not violating the school's smoking policy by leaving school grounds to smoke. Therefore, the school should not be able to suspend you for a violation of school's smoking rules. According to the rule book, there was no violation. I do not believe you should be held liable for the school's error and omission.
If the rule book said, for instance, that no student can wear the color purple, and you agreed to that rule, then you would not wear the color purple. If one day you wore orange, however, and the school suspended you for wearing orange because they forgot to mention in the rule book that orange couldn't be worn either, it would be just as unfair as the current suspension you are facing. I think the fact that you were smoking is getting in the way of the facts for some people.
If you were in a debate class, you could very well win. I am not sure you will have much success with your appeal, but I wish you luck, just the same.
(Just an added note: Although some studies have reported that 90% of all smokers start smoking at or before the age of 18, the legal age in most states, including Connecticut, is 18, and if you are under 18 and smoke, you are committing an "incorrigible act", or an act which is unlawful for kids but not for adults)