Complex sentence: According to the revised MOI policy, secondary schools were encouraged to adopt Chinese as the medium of instruction (CMI) starting from the 1998/1999 school year, of the secondary 1 intake of pupils, and progressing each year to a higher form at junior secondary levels.
Split into simpler sentences: According to the revised MOI policy, secondary schools were encouraged to adopt Chinese as the medium of instruction (CMI), starting from the 1998-1999 school year. This introduction of CMI started in the secondary 1 intake of pupils, and progressed each year to a higher form at junior secondary levels.