A diploma teacher who holds a teacher's diploma, has passed an in-service teacher training course or a non-graduate teacher qualification examination, has completed a primary school teacher training course or successfully completed at least one year of supervised teaching, or has equivalent qualifications, is eligible to be considered for promotion as an assistant teacher if he has worked as a diploma teacher in a primary school for at least five years and has completed a training course prescribed or recognized by the Director of Education. Diploma teachers without teacher training diploma or equivalent qualifications are also eligible to be considered for promotion to assistant teaching positions if they are employed before January 1, 1991.