They were alarmed at the long list of skills and knowledge found in many state mathematics standards. Quoting from their workshop essay:
In every grade, the mathematics curriculum needs to be carefully focused on a small number of topics. Most mathematics instruction should be devoted to developing deepening mastery of core topics through computation, problem-solving and logical reasoning.
They are recommending focusing on whole-number arithmetic and place value in the early grades, measurement being an important, closely connected theme. After mastering that, they said focus should next be on fractions & decimals, and then onto percents, ratios, and proportions.
This, in my opinion, sounds almost obvious.
But if you read some state standards for mathematics instructions, they abound with various objectives and skills - tons of stuff that students supposedly need to master on every grade.
Don't lose the forest from the trees (or the numerous leaves even). Keep your focus. Not every goal on those standards is as important as some others. These mathematicians would like to see state standards change - they are not a good guideline to build your math instruction upon.
The essay makes good reading overall: What is important in school mathematics?