There's no single "worst" school in Philadelphia. School quality is complex and depends on many factors, including test scores, graduation rates, student-teacher ratios, resources, and the specific needs of the student population. Different ranking systems will produce different results, and what constitutes "worst" is subjective and depends on the criteria used. Furthermore, a school's ranking can change year to year.
Instead of focusing on a single "worst" school, it's more helpful to look at resources that provide information on school performance in Philadelphia, such as the Pennsylvania Department of Education website or independent school rating organizations. These resources allow you to compare schools based on various metrics and choose the best fit for your specific needs.