Anything that might detract from doing that effectively and being taken seriously in the classroom just isn't going to cut it. But I also like it that you care enough about us to try to look nice. You see, administrators will often interpret a new teacher's desire to be a professional by whether or not that teacher looks the part. They often like it when you dress down, but they also appreciate it when you usually look neat and professional. It sends the message that they are worth looking nice for and that what you have to teach is important enough to you.
Children are like wet cement.
Whatever falls on them makes an impression. I remember a junior high school teacher I had for social studies who always wore purple sweatsuits. Kids can be mean. But they aren't dumb. We picked up on her message that we weren't worth the time to dress nicely.