Drawing upon his experience, more than 60 years ago, as a psychometric support person to a very special teacher of brain damaged children, the author of this article reflects on the productive use of educational assessments and data from them to educate - assessment in the service of learning. Findings from the Gordon Commission on the Future of Assessment are referenced to advocate for the position that educational assessments can and should be used to inform and improve teaching and learning processes and outcomes. The author argues for this counter intuitive claim, educational assessments and the data that are produced by them can be used in the service of teaching and learning. The argument draws on logic and emerging existence proofs. The second part of this article is devoted to brief descriptions of those existence proofs, half dozen emerging and established models of educational assessment transactions that are embedded in teaching and learning programs with the intention to improve both the teaching and the learning. This article does not include empirical evidence that either of these ends is achieved.