I mentioned other girls because computer science is considered to be a major for boys in most people's minds... I want to break this kind of prejudice :)
:D ... okkkkkkkkkk... but it sounds a bit odd there and therefore I wish you left that out :)
as you have to shorten it, dont be too kind to your own words. u can actually make the same point with more concise sentences.
I think maerd2012 is right. You need to remove certain phrases or words though you don't have a heart to do so. Try and avoid lines that have repetitive ideas.
OK.... here's my help;
"Drop it! This is not for you girls!" After seeing my score, the boys laughed at me, the only girl in computer science club.
"Hey! this is not for girls!", laughed the boys at my poor score. .... I took "only girl" part to the next line;
"Maybe you would better reconsider your choice. You know, most of the members in our club have learned programing for over four years but you have just started it." My teacher tried to dissuade me in a friendlier manner. I had longed to learn programing for years but my score... Embarrassed, I did not know how to response.My teacher smiled comfortingly, " Well, you can think it over. Just if you drop the club, you may have more time to learn something else like math. You are really good at it."
.... I guess the part in bold you can leave out because the teacher's intention is already expressed by the previous line. It sounds repetitive;
"Why not you reconsider your choice? Most of them are senior programmers who learned programming for over four years. You just started only",my teacher said politely. This is what I longed for, but my poor score messed it up. I, the only girl in the computer science club, was lost for words to respond.