Most Japanese people do not talk like how girls in anime do. Most anime females have really high pitched and "cuteified" tone of voice. japanese is a language that when you say words with higher pitch or put emphasis on differwnt words it can change the meaning. So watch out for that. In anime i think its implied about what the character is saying but it isnt normal for a japanese person to have a high voice like that haha! Its all about being kawaii,and high school girls have the same slang yes. Its very informal though—not professional so dont say things to just anyone on the street,mainly only to close friends and peers. :) hope i helped.

Hi Ellie, yes there may be difference in many cases. It depends on character and anime. Some characters speaks dialect or use unique intonation or phrase, but some anime character speaks similar to real languages.