Take Coke for example. There is, of course, the famous formula for Coke Classic, which at one point was changed with disastrous results and quickly brought back (which is how we now have Coke Classic). One may assume that Coke's enormous success is the result of THAT formula, and I would agree that MOST of Coke's success is due to that formula (and outstanding marketing/branding), but stop for a minute ans think about ALL the other flavors/formulas for Coke that exist today - Diet Coke, Caffeine Free Coke (and Diet), Cherry Coke, etc....
For students, teachers, and schools, success has never been nor will it ever be the result of finding THE formula. Success, over the long term, may actually be the result of providing enough diversity of experiences. No two schools are ever exactly alike. To design and use a system of education that relies on THE formula will never produce the overwhelming success we expect and desire for our students.
However, the key to making great FORMULAS is in maintaining enough of the basic ingredients to make sure the product is still recognized as that product. After all, while there may be dozens of varieties of spaghetti sauce, they all include tomatoes. Without tomatoes, I'm not sure it qualifies as spaghetti sauce.
This begs the questions, what are the core ingredients needed by students to find success, needed by teachers to support student achievement, and needed by schools to create environments conducive to growth? Does the debate over educational reform and effectiveness focus too much on finding THE formula instead of embracing the fact that there are FORMULAS for success - all of which have tremendous value?