Ranking is nearly meaningless. eg compare these:

School A - full of underachieving kids that are pushed to get avg grades

School B - full of avg kids getting above avg grades

School C - full of smart kids getting top grades

School D - full of smart kids getting nearly top grades, but soft skills, nice personalities and VIP friends

School E - Mix of kids getting relevant grades

Which is the best school for each kid type? They're impossible to rank. Many schools with top grades are only there because they kick out failing kids, not because they're better at teaching. Many schools are rated good because they can improve grades, but you wouldn't want to send a smart kid there. Many private schools sell themselves on creating well rounded kids, not necessarily good grades.