Bob Shepherd, a frequent commenter here, has been a curriculum writer, as assessment developer, a publisher, and a classroom tea her. As frequent readers of this log know, he is also a polymath, with a broad, nearly encyclopedic range of knowledge.

In this essential post, he explains why standardized testing is invalid and useless for accountability purposes.
They do not measure what they claim to measure.

Here is a brief excerpt from a brilliant explanation:

Nothing that students do on these exams even remotely resembles what real readers and writers do with real texts in the real world. Ipso facto, the tests cannot be valid tests of actual reading and writing. People read for one of two reasons—to find out what an author thinks or knows about a subject or to have an interesting, engaging, significant vicarious experience. The tests, and the curricula based on them, don’t help students to do either. Imagine, for example, that you wish to respond to this post, but instead of agreeing or disagreeing with what I’ve said and explaining why, you are limited to explaining how my use of figurative language (the tests are a miasma) affected the tone and mood of my post. See what I mean? But that’s precisely the kind of thing that the writing prompts on the Common [sic] Core [sic] ELA tests do and the kind of thing that one finds, now, in ELA courseware. This whole testing enterprise has trivialized responding to texts and therefore education in the English language arts generally. The modeling of curricula on the all-important tests has replaced normal interaction with texts with such freakish, contorted, scholastic fiddle faddle. English teachers should long ago have called BS on this.

Open the link and read it all.