I don't know how we can fix schools if we don't have a meaningful measure by which to compare their performance longitudanally and latitudinally."We" don't have to measure, meaningfully or not, performance. The error here is conflating the owner of schools - "us", though it should not be - with those that they serve - individuals, as proxied by their parent(s). "We" are not "us", so to speak. (This is one of the design flaws of the English language.)
Education is no more important than eating. Imagine your statement cast as one about the food market: "I don't know how we can fix food-providers if we don't have a meaningful measure by which to compare their performance longitudanally and latitudinally."
That's just silly. As if we might compare Steve the Farmer's job performance against that of McDonalds as against Chez Snob as against my kitchen abilities. All are involved in food-production. All are incomparable. One size does not fit all. There is no reason to assume it does, or should.
Of course, food production in this country is not broken and does not need to be fixed. Food production is private. Education is public. Therein lies the solution if we care to see it.
Returning to the production of food: food production that involves the market is "tested", in a sense. It's tested on the market. Businesses that make money continue and if they are successful enough, may expand. Those that don't make money eventually fail. But this has nothing to do with any standardized test.
The solution to the education crisis is not standardized testing. It is competition - market testing. The solution is possible only with more liberty - ideally, completely privatizing education; less ideally but practically, instituting voucher programs. Educational socialism doesn't work; and it cannot work in the long run for the same reasons that socialism always doesn't work. Why do we accept as obvious that the Soviet Union failed economically, but then puzzle over the failure of our daycare prisons? If there's anything puzzling, it's that, not the failure of the schools.
With educational freedom, "we" don't need to test. "We" - the collective we - can leave the evaluation of results up to "us" - as individual parents. Tests will continue to be a part of that, of course, for some or even many schools and parents. But there are many other aspects of education that are not on standardized test, and cannot be.