Northwestern's high ranking comes from last years success and this years potential. They did not lose much from last years team that lost only 3 matches I believe. Plus they added a high quality coach in Nick Finotti. So, preseason they started out high in the rankings, and have not had any results that should make them fall. They lost in pks to Chapin, not a bad result and have beaten a decent AC Flora team and on Friday night beat Lexington who was number 7 in the state i believe. I hope this answers your question. I do not know of a strength of schedule ranking on this site, but i do know every major 4A school, irmo, sumter, wando, dorman, etc. plays weak schools. its just the nature of high school athletics.