Denis's answers are generally spot on. However, there are possible deviations: (a) If the speaker said #1 immediately after talking about another boy in his or her partner's class, the context is there that would allow for this sentence to be correct. e.g. "John is pretty damn tall. I am taller than any other boy in your class." (b) #3 also might not be correct if the speaker is a girl, unless the situation was similar to (a) above).

The question revolves around the use of the word "other". ---- #1 In this sentence any "other" boy in your class means: any "of the remaining" boys in your class. ----In order for any boy in your class to be any "of the remaining" boys in your class in relation to me, I must also be a boy in your class. ----But I am not in your class, otherwise I would say "my" class or "our" class or "the" class. Conclusion: I am taller than any other boy in your class....... does not make sense. ---- #2 The word "other" is removed from sentence #1. I am no longer another boy in your class. I may even be a girl in this case, but I am still not in your class. I am taller than any boy in your class....makes sense. ----#3 The word "your" is replaced with the word "my". I am in obviously in my own class. I am taller than any other boy in my class...this sentence now makes sense

So, narrator "I" is Person A, his class is Class A. The other person "your" will be Person B, and his class is Class B. I believe #1 is wrong because, the Person A is not in Class B, so the "other" is unnecessary. For the last sentence, you can use "other" because Person A is referring to all the other boys besides himself in Class A. I don't know if its right or not, but that's my take on it.