The more I read people's experiences on the board, the more concerned I am with who is teaching our children. That first teacher did, indeed, have a harmful effect on your son's ability to write. It is good that he is no longer in the program.
If we really think about the process of writing development, we can begin to see a way to help him. There may be something that he does not feel comfortable with and, as a result, we may be able to pinpoint the problem and get him the help needed.
Overall, I agree a lot with what has been said. Let's take a more diagnostic look at things on top of it and see if we can pinpoint the problem rather than guess at it.
Begin with something simple. Just ask him to draw a line. He might look at you strangely, but thank him when he's done and don't ask him to do more. As he's doing that, look at the following:
1) What hand is he using? I'm curious if the teacher that kicked him out was also trying to force him to use his right hand. Let's face it - she does not seem to know a lot about child development if she is putting a child in time out for not coloring. This may be a very real factor.
2) How is he holding his pencil? From experience, a 4 year old should be able to have a decent proper grip on the pencil. Not perfect really, but should be able to hold the pencil normally. Either way, NOW is **NOT** the time for instruction. If you notice him holding it wrong, let him do it that way for now. I will provide some exercises later to help in this area.
3) Watch how he draws the line. Is it fast and careless? Is it slow and meticulous? If it's slow and he's really trying to get it right, that may bring light to the issue. He may be more concerned with messing up and doing it wrong than he is of enjoying the process itself. Many children are like that.
If it's fast and careless, it may be that he's bored and unchallenged with it. Notice I said "may." That's not a definite diagnosis based off those, but it at least points in a direction to go with more investigating.
What do you do in these situations?
#1- Using left hand. Again, he may have been forced to use the incorrect hand. If he is using his left hand, when you are working with something for writing, be sure to always put the writing tool near his left hand. Even reach past him to put it there.
#2 - incorrect pencil grip. Your child may feel awkward with actually holding the pencil or crayon comfortably. Do other activities that build up the fine motor skills of these three fingers. Anything that is more natural to grab with the index finger/middle finger together clamping down onto the thumb is what you want to look for. Some ideas:
--There are soap dishes out there that are made of rubber and have small suction cups on them that are the ideal size for beads. Get those and get some beads. You can make up a game to go with it like Tic Tac Toe (you'll have to make up a game that fits the materials you have). Show your son that the easiest way to put them on there is with the pencil grip. Don't call it that...just show him how you do it. Let him decide to do it or not, but every time you go for a bead, put your fingers in that pencil grip and open and close them a few times while you look and decide which bead you want, then reach down and grab them. Model it every time and he will start to do the same.
--Some puzzles have nobs on them to pick up pieces. It is sometimes hard to find a knob that you use a pencil grib on naturally, but if you find one, grab as many as you can.
#3 - How he draws the line. This can lead so many ways, but let me just say that what you want to keep doing is observing and taking notes. If he draws it and seems concerned and focused on how it looks, does he do the same with other things where he doesn't want to make a mistake? If so (or if not), you'll have to keep observing to find out exactly why that is. Think of yourself like a scientist that goes out in the woods to study nature. The scientist does not disrupt the lion, but rather sits back and observes, makes notes, and tries to identify what behavior it sees and why it behaves that way. From there, you will understand further how to help.
As far as the attitude towards writing is concerned, I have a feeling that if there is no other reason, patience is the key. He's had a bad experience with writing at his last school and I do not expect him to come rushing into it excitedly. Now is the ideal time to begin teaching him writing and giving him opportunities to draw, but if a child has a bad experience with something, they tend to stay away from it for a while until they feel comfortable (don't we all?).
I hoped I help. Above all, if my ideas prove no results, just keep observing. Observation is always the key to understanding a child's behavior and it's a idea the first teacher at the preschool obviously missed.
Matt