At ASCD in March, I saw more than one presenter make the 20th Century = Bad vs. 21st Century = Good distinction. Trust me, there is nothing which will open your eyes as quickly early on a Saturday morning as slides like these (taken from Session 1118):
Good teachers have been using things like self-assessment and questioning to evaluate student products (including case studies and portfolios) long before the year 2000 (or 2001, if you're a stickler). The cognitive demand of a "selected choice" item has nothing to do with which year it was written (not to mention you can write an incredibly bad item no matter the cognitive demand). And best practices in assessment are just best practices---whether or not you use technology. But as I look at these slides, and consider the similar proselytizing by other presenters, I think it's an interesting study about what happens when someone's chocolate lands in someone else's peanut butter.
Cries for 21st Century skills, first heard from the EdTech camp, seemed to spring from a need for credibility. Techies didn't want to be seen as people with toys---look, kids can learn with these things, too! And they can learn better...faster...stronger! And while that shot did land in the Instructional camp, it hasn't grown in the way EdTech hoped for. In fact, it is being returned to EdTech in a twisted and stunted manner like Dorian Gray and his painting. I'm both amused and horrified by this turn of events. Techies are ready to abandon the term (we're already more than a decade into the 21st century) while it's just turning red hot in the rest of the education world. This time warp means that there will never be any sort of agreement about what the term means---or its relevancy to the classroom.
I think that, as with any edu-fad, this term will fall out of favour soon enough and we can weed out the definitions at the edges. What we will likely be left with is some sort of agreement about a set of skills that cross disciplines (critical and creative thinking, collaboration...). However, at the rate we're going, that might not be until the 22nd Century.
P.S. Today is the 50th anniversary of the beginning of construction for the Seattle Space Needle---built for the Century 21 Exposition in 1962. We've been using the 21C term a really long time...