Complex sentence: The aim of Big Writing is to advise schools on how to raise a child's attainment in speaking, listening and writing and the method is currently used by numerous schools, primarily in the UK but also overseas.
Split into simpler sentences: The aim of Big Writing is to advise schools on how to raise a child's attainment level in speaking, listening and writing. The method is currently used by numerous schools, primarily in the UK but also overseas.