Even though your child is ready for school, you still need to be the main source of discipline in your child's life.
Whenever your child refuses to carry out your instructions, or misbehaves, they are testing the limits of your rules and how much they can get away with.
If you show any inconsistency in discipline, your child will exploit this the next time she feels like misbehaving. If your child misbehaves in the same manner repeatedly, it is also a method of testing whether or not you will give in and allow her to get her own way.
Aggressive behaviour is normal at this stage and there will usually be specific situations that trigger aggression in your child. You need to act fast and make sure your child understands that hitting, kicking, or biting is wrong. Your child must also be aware that there are consequences to antisocial behaviour. While disciplining your child is important, do not over-do it with minor things. This way, the important infractions get the attention they deserve. Avoid getting involved in arguments over matters that cannot be resolved, such as eating habits.