7-8 days ago, ypn did something to their targetting engine, for both contextual and category targetting. some people are reporting a drop in ctr while others are reporting an increase. i cant answer directly regarding education category, but your timeline is about right.
yes, it actually all started back at their last update, and I think they are continually working on it....last week to get their act together before they go public!! lol.
I think it has to do with their categories. They aren't for sure how much to take it seriously anymore. Sometimes they use both ctr and categories to target, and that gives me much better earnings. Sometimes they just show the highest paying ads, regardless of if it is receiving clicks or not. That gives me less money of course. Then sometimes they just show the category... which is OK, but not as great as the first. Then they just show relevant ads to the page and doesn't include data from the whole site. That is OK sometimes, but not OK others. They just need to find a midpoint now. Once they incorporate all their knowledge about the site, category, click through rate and earnings... they will definitely have a gold nugget.