Very good points by specialmom!
The fact that he responds to positive reinforcement is huge. Work it as she suggested.
Also kids of his age need immediate consistent discipline. By switching to different punishments, it almost like he is controlling you. Realize that to change his behavior, it will take about 3 weeks of the same consistent discipline. "SOS Help for Parents," by Lynn Clark will give you a good consistent measure to follow. Combine that with specialmoms suggestions, and you will see changes.
By the way, if you go back several pages looking for things like "out of control 4 year old", you will see that you are not the only one having these problems. You will also be able to see other good suggestions. Best wishes
Okay, take a deep breath! He's only 4 and it will be alright.
You hit the nail on the head--------- he's got a bad role model. The only way a 4 year old knows cuss words is if someone cusses around them. He's talking harshly, being rough, etc. because maybe that is how dad talks. So let me ask you if you have any kind of contact with his father? Hopefully you have put aside all of the things between you two and have focused on just co parenting your child--------- so you two are civil and can communicate. If that is the case------- I think you can talk to him about how your son is acting at school and that you are concerned about it. Maybe he could give up cussing and act as he would like his child to act at school. This won't solve the problem but it will help. If you dont' have a good relationship with his dad---------- work on it. YOu need to be friendly enough with him that no one gets defensive and all do what is right for the boy.
Second, punishing after the fact for what happens in daycare is ineffective. It never works. What do THEY do to address it? Punishment with a 4 year old must be immediate or it isn't worth doing. So find out how the school handles things. Go and observe for a day-------- it is worth taking a little time off of work to find out what is going on with your own eyes.
Then at home--------- think of it as teaching him. Role play or act out scenarios that happen at school and you act how he should act. Give him options for his behavior.
Last----- you found that he DOES respond to positive reinforcement and a reward system. This is good news. Just tweak it a little. Instead of a prize-------- you could do one of two things. He could get beans in a jar when he does as you ask or is acting the way you desire and you want to reward him, etc. He then can put the bean he earns in a jar. When he gets to a certain number---------- he gets to choose an outing of his choice such as watching his favorite video with you or whatever or a small prize if you want to go there again. I'd say 25 beans is a good number to get to for that. Or you could do coins and give him coins to put in his piggy bank as he does things the right way or behaves, listens, etc. and when the bank is full, you open it together and count the money. He has to save half (we take our 5 and 6 year old to the bank and everything) and then he gets to use the other half to buy himself something. I may throw in a buck or two more to help but they love to shop.
Give him two choices whenever possible. You set the choices and he has to decide between the two which gives him a sense of control and he will be more willing to comply. Very effective tool with kids.
Okay, good luck