why do they send home a different child?

Every morning I wake up my two oldest children and help get them ready for school.  My daughter is always grumpy - mainly because I have laid her clothes out for her - and obviously what I have picked isn't "stylish" enough for her.  (whatever, you're in 3rd grade for goodness sake!)  Then there is my 5 year old boy.  He gives me a big hug and kiss, tell me how much he loves me and wants me to walk him to the car and help him get in his seat before his dad takes them to school.  He is shy and won't talk much about what he will be doing at school that day, or what happened the previous day.

Then 3:00 comes and I pick them up from school.  My grumpy child has calmed down - until she gets in the car that is.  However, by shy, sweet baby has turned into a demon child!  I swear he is whining, yelling, pinching his sister, telling me I am not his friend because I won't take him to the store....  WOW!!!  I realize a lot of this is because he is exhausted from being in school all day, no nap, no real down time,  (can you imagine how that affects a child's brain?) but why can't I have the sweet child in the evenings when I can spend some time with him? 

I sincerely hope he becomes accustomed to this new routine soon.  I really don't know how much more I can take -- it has been a looooong ride home for the last 3 days.