Everyone would love to wear sweatsuits and flip-flops to work but, unless you work from home where no one can see you, sweatsuits and flip-flops are totally inappropriate. When you work in the professional industry, especially in a school, you need to make sure that you are making the best choices for your wardrobe.
When you teach, you need to think about comfort. Teachers move around a lot and are often standing or sitting for long periods of time. While sweatsuits are definitely out of the question, comfort is key. Think about wearing a loose-fitting but well tailored pieces. Your clothes should not be to casual but they should not be sexy or provocative either. You should not wear clothes that are to tight or hug your curves while you are teaching.
Teachers have a bad reputation for dressing hopelessly out of style. You should try to appear with it but not follow every style that graces the runway. Look for fads that would flatter your figure but would work in a professional environment. Wearing the same clothes as your sixteen year old students is not a good idea. Remember that you are accountable for guiding young and impressionable children. If you are are right out of school you need to be extra careful. Students and parents will be thinking that you are inexperienced and do not know what you are doing. You should dress for the part. If you are dressed professionally people will take you seriously.
Leave the sleeveless shirts for the weekends. Sleeves will always be considered a more put together look. And if you are male teacher wearing shirts without sleeves, then you should leave the shirts all together.
Finally, make up is not always your friend. There are times and places for wearing a smoky eye or bright viberant colors but the work place is not one of them. Most middle school and high school students are learning to play with makeup and usually do so in the excess, you do not want to look like one of your students.