A reader sent this comment:
Here is my take. Our school in NYC used an online, computer based reading program for the first time last year. Some of our students were clocked in as reading 600 articles and having their lexile scores increase by 4 grade levels. At the end of the year, the representatives from the program came to the school and gave an assembly for all of the students who participated; giving out prizes and accolades to the most prolific readers. One student in particular kept going up to the stage to receive accolade after accolade. NYS’s ELA and Math scores recently came in, and guess what? – she did not show any growth from last year.
Here’s the problem: When I observed the students who were clocking in an inordinate number of articles, I noticed that they were just answering the questions in order to get the “rewards” that the system gave out. I asked them why they weren’t reading the articles. Their response was that it was boring. You see, it’s like a video game. They are doing it for the rewards that the system produces; not for the enjoyment of reading.
There is always room to game the system. Ask any video game player about “cheats” and they will tell you. Kids will always find a way to game the system. Online publishers will always find ways to game the system as well.
Diane Ravitch's blog 
This is shocking to zero teachers and students. Was anybody unfortunate enough to have classes that assigned textbook worksheets? Remember how you just scanned until you found the bold word that matched your worksheet bold word, and filled in that blank with an answer that made no sense to you? Or was that just me?
Not just you! (It’s also, imho, over-testing is the reason many kids might tend to think in a superficial way. But that’s another post.)
My kid doesn’t like online adaptive assessments. She likes knowing there are 50 questions in 40 minutes. She hates tests that give you many more difficult questions when you answer correctly. The test seems to go on forever.
So, one time she decided to hit buttons randomly and get a bunch wrong. Then the computer spit out fewer, easier questions, and she was able to finish the test at last.
You can imagine how some of my ADHD students responded to those tests: “You mean I have to do more if I’m right?!”
“On-line, computer based reading program”. Reading those words made me a little bit sick to my stomach.
I see a great business opportunity here for some young hacker to hack into these tests and find the answer keys and/or even totally change the tests. Payback is a bitch!
I can see it happening.
Kahn Academy has also experienced this. The kids are not stupid. We set the rules and they will figure out how to game them. It’s just a lot harder to track it in the virtual world than when there is a competent, live teacher in the room.