Do we need a dress code for public school teachers?

It's common knowledge that according US current educational policy there is no dress code for teachers. But in some school districts of the very West Virginia local school boards have had to ban low-cut blouses and blue jeans for teachers. Thus, there are concrete attempts to institute a dress code for public school teachers there.
And only local teachers union knows that such dress code has appeared in Kanawha County Schools, for instance, under pressure of Muslim students' parents, who demanded that teachers must "focus on education instead of drawing students' attention wearing tops or skin-tight jeans" (dailycaller.com/2014/01/01/west-va-teachers-union-). In this case I cannot but agree with president of the American Federation of Teachers, Christine Campbell, who calls such dress code "an unconstitutional encroachment on human rights of teachers, as it infringe on their freedom of expression"! That is it! Why, on earth, should we conform to Muslim standards of life? They've arrived at this country and must integrate into our society! Otherwise let them buss out!