According to EduBase, SHHS last year had 92 girls in the last year of GCSE and only 54 girls in the first year of sixth form.
www.edubase.gov.uk/establishment/census-data.xhtml?urn=100076
Given that SHHS claim to admit at least a few students at sixth form, more than 30 girls, or 1/3 of their GCSE students, must be leaving each year for a different sixth form. This appears to be a much larger fraction than at SPGS, NLCS, CLSG, etc.
Does anyone have information about where these 30+ girls are going and why so many are leaving? I'm told that many girls and/or parents seek a coed environment at that age but, again, it seems like other top London girls day schools hang on to far more of their students.