Any qualified teacher filling one position on staff for a continuous period of six (6) days or longer as a substitute teacher shall be paid according to his or her qualifications and experience according to the salary scale beginning with the sixth (6th) day of teaching in the same position. This rate of pay shall be retroactive to the first day of the extended teaching assignment and continue in effect until the end of that extended teaching assignment. However, if the duration of the substitution is known to be beyond twenty (20) continuous teaching days, the substitute teacher will be signed to a Limited Term Contract and paid a teacher per diem rate according to the provisions of Article 6.01, beginning on the first day of teaching. Substitution days cannot be accumulated from one assignment to another.