Complex sentence: The SRC organise "Spirit Week" during Week 10 of Term 2 to give the girls a chance to lose the seriousness stemmed from half-yearly exams, and most of all, promote and increase school spirit and a sense of belonging within the school community.
Split into simpler sentences: The SRC organise "Spirit Week" during Week 10 of Term 2. The main purpose of Spirit week is to give the girls relief from the probable stress stemmed from half-yearly exams, and most of all, promote and increase school spirit and a sense of belonging within the school community.