Too many people confuse measurement with assessment as if they were the same thing.
They are not.
Some things are made to be measured. For example, I'm 6'1''. Height is a one-dimensional thing that can be reduced to a measurement in standard units. We need standard units for height or we would have all kinds of mass confusion.
Some things in life, however, are not made to be measured. While my height can be accurately described as 6'1'' without debate, my personality, character, intelligence, athleticism and learning can not be meaningfully reduced to a symbol. When we reduce something as magnificently messy as learning to a number, we always conceal far more than we ever reveal.
The most important things that children learn in school are not easily measured. The most meaningful things in life may, in fact, be immeasurable. The good news, however, is that the most important and meaningful things that we want children to learn and do in school can always be observed and described. This is precisely why it is so important to remember that the root word for assessment is assidere which literally means 'to sit beside.' Assessment is not a spreadsheet -- it's a conversation.
Testsandgrades should be replaced with projects and performances collected in portfolios.
When student learning is made visible to parents through portfolios, blogs, student-led conferences and parent-teacher interviews then they are not nearly so desperate for less meaningful information such as testsandgrades.
This is my 16th year of teaching in public schools. I threw my gradebook away in 2006. For those who are interested in learning more about what school and learning looks like without testsandgrades, you can read my chapter from my book for free here. And you can read all of my blog posts about abolishing grading here.