You already know that everyone learns differently. You already know that each kid has different interests, and you know that kids learn at different rates. So you know, intuitively, if you set up school to be a competition, it will not be close to a fair fight.
You won't have all the math kids competing against each other in math and all the artists competing against each other in art. You actually have the math kids competing in art and the art kids competing in math, because the idea of school is not only competitive, but also pushes the idea of well-roundedness.
1. Testing gives people a way to rank kids.
2. Report cards give parents a way to rank themselves based on how well their kids learn.
3. School measures IQ not only with testing, but by setting up discrete subject matter that requires basically one type of IQ. For example, school does not measure emotional intelligence. Only the intelligence to memorize facts.
The best way to extract your mind from the hamster wheel of competitive schooling is to look at the chart that the Atlantic published about how parents in different countries describe their children.
Most parents in Australia describe their kids as happy or easygoing. Parents in Italy describe their kids as well-balanced and even-tempered, and parents in the Netherlands say their kids have a long attention span. Parents in the United States overwhelmingly describe their kids as intelligent.
Ironically the traits that parents in other countries use to describe their kids are actually the traits that help people succeed as adults. But the traits that American parents obsess over are traits that actually have no correlation to happiness or success in adult life. The American school system effectively translates parent concerns about their kid into a daily routine that focuses on those concerns. Which would be great if the concerns correlated to success or happiness.
United States parents are alone in their need to tout their kids as having a high IQ. It doesn't take a high IQ to recognize that parents are overly invested in their kids' reflection on themselves.
Telling people about their kids' kindness and happiness will help the kids to see themselves that way. Telling people about how easy their kid is to deal with, which is what people do in Spain, will reinforce the idea between a parent and child that their relationship is thriving.
You don't need to wait for schools to change their focus to something that actually matters in children's lives. You can change that focus yourself by taking your kids out of school and emphasizing what parents in other countries emphasize, which is what makes a good person instead of what makes a smart person.