Teachers employed under contract on a part-time basis shall:
(a) be paid according to their qualifications as established in Article 3.02 and 3.04;
(b) be paid on a rate based on the fraction of time employed;
(c) the service of a part-time teacher shall be accumulated in the proportion of actual percentage of time employed in each school year. Whenever a part-time teacher's accumulated service equals the equivalent of one full year or more, that teacher shall be reclassified to the next higher step of the schedule, on September 1st or January 1st next, whichever comes first.