How much attitude from you 2nd grader is too much?

It seems as if your daughter was as sweet as can be,until she entered preschool. As soon as she got into preschool,her attitude really started to stink. I understand,that some kids are naturally going to have a little more attitude,but let's move on-she's now in second grade,and she's starting to do things that are driving her dad and I absolutely crazy! She's not showing respect towards her dad and I,and is always making snide/disrespectful comments,lies more often than not,but for the most part (when not lying or having horrible attitude! is a great child in most other senses). I thought this happened in teen years,not in 2nd grade? Was I wrong for thinking that,and have any of you other moms/dads had to deal with this?