The author isn't Valerie Strauss.

"Decimals" is (in the US at least) a common way of referring to decimal fractions (that is, numbers represented like: 12.345) vs the whole number or integer representation that the students would already be familiar with (like 12) or other fractional notations like 6 7/10.

I am under the impression the author of the article is Valerie Strauss and she is presenting a small piece critique by Christopher Danielson and Michael Paul Goldenberg at the top of her article. If not, there is a problem with the placement of her name at the end of it.

As for the abbreviation presented, it is just terrible and is used in article while accusing others of lack of Pedagogical Content Knowledge.

So you believe she speaks about herself using "We" instead of "I"?

Her contribution is the first 2 paragraphs, the rest is the critique from Christopher Danielson and Michael Paul Goldenberg.

Edit: And please explain, how is the abbreviation terrible, because I've clearly missed something.

"We" may well be used instead of "I" and at the end it reads "By Valerie Strauss". The attribution is placed in a random way all through the article and that threw me.

The abbreviation is terrible because in the article it is used in reference to "the numbers to the right of the decimal point"; "decimals for short".

To the first point: The first and second paragraphs are italicized, clearly distinct from the rest. This is intended to show a distinction in voice (authorship). The content of the first two paragraphs are nothing but framing for what follows. You're either being excessively pedantic, or have elected not to read the article to have so much difficulty in recognizing authorship of the 2 parts.

To the second, I still don't see what makes that terrible. It's saying, decimals is short for decimal fractions, and provides a definition for decimal fractions.

Article starts with: "How well does Khan Academy teach? By Valerie Strauss", then "By Christopher Danielson and Michael Paul Goldenberg" on top of their contribution. At the end of the article there is a : "By Valerie Strauss". So attribution is displayed twice before text blocks and once after text blocks, if you don't see the failure in that, I am so sorry. I don't know how pedantic it is to confuse voices when they are attributed in two different ways when it is clear that the second way is the most common, but I will leave it to you to quantify it, not that I care for it. But do keep up the winding, you will be on to something, sometime soon.

Second: "Comparing decimals. Decimal fractions (decimals for short — the numbers to the right of the decimal point) are a notoriously challenging topic in the elementary math curriculum."

For the last time, decimals are NOT the numbers to the right of the decimal point like stated. "decimals" is being used for a subpar abbreviation of decimal fractions AND the left side numbers to the decimal point are a part of it, unlike what said authors state. Someone with pedagogical concerns should be awake when stating stuff like this and if you don't see the mess that is, that is your own problem. I have stated this already.