My 3 year old does the same thing and I know how you feel! The only trouble is I haven't found how to make him stop doing it. Reprimanding him definitely doesn't work. If anyone has any ideas, I'm all ears!

Isn't this in the same department as whining? My kids were all big whiners at that age and I clearly remember asking them to repeat everything in a normal tone of voice. It wasn't a fast cure but it must have been a cure because they are now 10, 8 and 6 and none of them are whining any more!

You can try the CLeaR Method: Comment, Label & Reward. When she's NOT screaming or screeching, make a comment like this one: "I like the quiet voice you're using." Follow this with a label of some sort. For instance, "That's a big-girl voice." Finally, reward the correct voice as in, "Since you're such a big girl with a beautiful big-girl voice, I think you should be allowed to watch T.V. with Mommy for a few minutes tonight" (use any appropriate reward that she'll enjoy). If your daughter has spoken in an unpleasant tone of voice, ask her to repeat herself in a pleasant tone and then use the CLeaR Method. After a few times of offering a reward, start to thin it out by using just Comment and Label for a few times without using a reward, then add the reward again, then use Comment and Label for a number of times without the reward, and so on, until you fade the reward out completely.  All the best,  Sarah Chana