Am I doing something wrong?

There is a girl in my class that I kind of like but she will only talk to me when we sit in maths together. I've tried to talk to her outside of class but she seems to go out of her way to avoid/ignore me. I've never done anything to make her upset or angry at me. Could anyone give me an insight into what's happening?

Edit: forgot to add...she tends to play footsie under the table and laughs ridiculously at what possibly could be my worst jokes of all time