(a) County boards of education in fixing the salaries of teachers shall use at least the state minimum salaries established under the provisions of this article. The board may establish salary schedules which shall be in excess of the state minimums fixed by this article, such county schedules to be uniform throughout the county as to the classification of training, experience, responsibility and other requirements subject to the following:
(1) Counties may fix higher salaries for teachers placed in special instructional assignments, for those assigned to or employed for duties other than regular instructional duties, and for teachers of one-teacher schools;