Complex sentence: Mount Saint Mary's School today stands in a district of Leeds traditionally known as "The Bank", which ahd become home to a large community of Irish Catholics who had emigrated to Leeds to seek work building canals and railways and as millworkers.
Split into simpler sentences: Mount Saint Mary's School today stands in a district of Leeds traditionally known as' The Bank'. By this time, The Bank also became home to a large community of Irish Catholic families who had emigrated to Leeds to seek work building canals and railways and as millworkers.