The selection of a professional dress is the right of an organization. However, if you are generally asking, then not at all! It is not necessary for any teacher to wear a Saree.
However, a teacher should wear very comfortable dress and he or she should not try to give much focus towards it for giving youthful looks. According to the standards of any International institution, the dress should be professional. There are a number of institutions which have issues regarding the dress of teachers and school boards often raise red flags for the inappropriate shoes, too casual clothes and skimpy outfits of the teachers.
Moreover, it has also observed that students never concentrate towards lecture of the teacher if he or she looks either very attractive or very awkward.
They should wear Saree only. Because if they some other things, we cannot enjoy them. If they wear saree, we can see their hips, sides and even navels if we are lucky.
From your question,,,,I think you are from Asia.....m I right????Yes I think that a teacher should have a professional look but its not the same as company dress...in companies the most appropriate are shirts but a teacher has to handle children and so a very very serious and professional look should not be there...Children must have a feeling that you are their aunt so that they should be frank with you...and secondly if students are supposed to be in a simple look,,,teachers should also.....m not saying this because m a student but because,,,so that students may take good inspiration from their teachers...so a good school must a have their teachers wearing sarees ...plz rate my answer