Is anyone else having this problem wih their 5 year old?

My 5 year old daughter started school this past year, and i recently gave birth to another daughter (now 4 months old). she has been acting out in school almost everday, and literally doesn't listen to a word your saying, but she'll stare at you while you talking and you'd swear she was listening to you, but when you ask her to tell you what she just said, she has no clue. Her teacher is frustrated with her and has asked me to take her for behavior modification, which is basically counseling and testing to see if she has a "learning disability". she isn't mentally handicap by any means, she's actually the opposite to smart for her own good. I've tried everything in the book disaplining wise, taken toys away, made her sit in her room, no desert, the list goes on. i know some of it is normal because of her age, but believe me the outright disobeying right after we tell her not to do something is a major problem.