My 3 year old started preschool 3 days a week (private sitter other two days) about 2 months ago. He did great (totally different from home) and his father and I were pleasantly surprised. However, this week he began being defiant, not following directions then kicked, screamed, and spit at his teachers. He was sent to the "principals" office twice in the past three days. We've taken away his blankie, bicycle, put him in his room for about 30-45 minutes each day. We talked to him about why this is unacceptable but we are afraid this might be the beginning of a new phase. Any discipline suggestions to stop this?