Attention moms of pre-teens HELP!

So my daughter just turned 10 yrs old is driving me NUTZ lately! Dont get me wrong she is a really good kid rarely ever has gotten into any trouble at school or gets into any serious trouble here at home. Her main thing is CARELESSNESS or plain out LAZYNESS maybe?? Since she has started school up again she has has alot of homework every night well some nights more than others. I always look over it and let her know if anything is wrong help her out ect.Well just about ever darn time I check her homework there are just plain out careless mistakes. She will ususally have the correct awnser, but say she writes her math problems so messy and fast you can hardly make them out. Her spelling she will have incorrect words when the words are written on the page in the question right before her eyes. I warm her of this all the time yet she continues to make just carelss mistakes. It is not even a matter of can she or cant she do things I will ask her what is wrong with this word she will say its spelled wrong and proceed to give me the correct awnsers, She can write neatly when she puts the effort in. I am just so frustrated I tell her your awnsers that are correct quickly become incorrect because of just dumb mitsakes! Is this normal stuff for a kid this age or what I am confused here? Then this morn right before she gets outta the car she says here mom you need to sign this its a note that she pinched one of her friends in P.E.! I was s upset she just showed me the darn thing instead of showing me last night then why the heck would she do that for anyway? GRRRRRR I am so frustrated with her I have taken privledges all the normal stuff it just seems like nothing really gets her to "get" it ya know? Any suggestions anything anyone??