A total of 575 students from the Associate Degree Foundation Program and the Associate Degree Program participated in this study. The two purposes of this study were to use the time series between/within experimental design to examine whether participation in co-curricular activities could (1) enhance student learning effectiveness and (2) have positive effects on the academic performance of self-funded sub-degree students in Hong Kong. It was found that participation in co-curricular activities could not enhance student learning effectiveness. Associate degree students were too preoccupied by the need to attain good academic results in the first 2-3 terms of study. Rather, this study suggests that student learning effectiveness is affected by the time factor. High learning effectiveness was observed in the middle of the academic year but relatively low learning effectiveness at the end of the year. (Contains 5 footnotes and 6 tables.)