Complex sentence: It is likely the ACC developed from an earlier groups known under differing names including,'The Combined Catholic Schools Association', which involved a number of schools conducted by the Christian Brothers and which held its first athletics meeting in 1902.
Split into simpler sentences: It is likely the ACC developed from earlier groups known under differing names. These groups included,'The Combined Catholic Schools Association', which involved a number of schools conducted by the Christian Brothers and which held its first athletics meeting in 1902.