You really need to get control now! My stepgrandson acted exactly the same way your daughter does when he was that age. He is 12 now and still no change in his actions because mom does not disipline . Mom was also in the service...gone for extended periods of time. I get the feeling that these children resent mom not being around in their lives and in turn act out. It's a lot easier to nip in the bud when the child is young, rather than wait until the teenage years. If young children are allowed to get away with hitting, etc. when they are little, what are they going to do to you when they are 15, 16, and older? You may end up seriously hurt, or in worst case senarios....dead. Don't laugh!...Listen to the news...it happens. I think getting a psycologist involved is a good idea...you need to get help wherever you can. I have read a good book lately that I think everyone with these problems should read...it really help me. It,s called Dare to Discipline. You can find it on website:
http://family.org I recommend it highly. Good luck with your daughter.
There's no way I can tell you with certainty why your son may be acting in the fashion he is. However, it is fair to say that, due to your deployment, you have not been able to establish a foundation with him which would set the stage for his learning impulse control and how to respond to limits that are set by parent, teachers, etc. The single most important thing right now is for you to employ a systematic behavior management plan, with time out as the basis for discipline. Try to obtain the book SOS: Help for Parents and you will see the sort of plan I'm recommending to you. A consult with a child psychologist would be useful to clarify what is occurring. You'll want to rule out that the behavior is symptomatic of a mood disorder, e.g., vs behavioral unrest prompted by the interruption in the parent/child relationship and the turmoil this can bring about for a child.
I'm sure the doctor will have good advice for you, but to address the sticker program you are using. Because your son is so young, the set-up isn't really conductive to success for him. He needs multiple opportunities through the day for success, or smaller chunks of time to be successful in. What i mean is (and hopefully the school will help/participate): use recipe cards or something else and break the day up into 6-8 chunks. (2-hour blocks, or morning 1, morning 2, lunch, afternoon 1, afternoon 2, etc). Set a goal like, 5 stickers/day and have a weekly reward for successful days. If he fails to earn them, he can lose priviledges. As he gains success, continue to reset the goal weekly, a little higher until he can achieve 90% success.
This is the exact advice I got for my son (I too started with the good day/bad day stickers) and the school advised it was best to have smaller time periods. They were right. It worked wonders for my son once he could see that a little effort worked (he saw regular successes all day long); one slip up didn't ruin his whole day's effort; he was excited to do well on the program and eager to meet his goals, once he got the hang of it.
good luck.