She said that she could not remember what she was taught in classes and this is why she was in special education classes. It is not sure why she could not remember information. It could be from a disability or from a lack of interest in the subjects. I am more inclined to believe the latter one as she seems to remember very well some subjects (food, fashion, Miley Cyrus, etc) and not others. Basically, if it does not interest her, she has no use of the information (history, geography, science, etc).In a video from the early days of her channel she admits to being in special ed all throughout middle and high school.