I got this idea from the game The World Ends with You. In that game, you can read people's thoughts all the time, but usually they're not thinking anything useful.

You see, if Lilly tried to use her power to cheat on a test, she would probably waste all her time concentrating and only hear "oh no, I'm running out of time!", "I'm glad I studied for this," etc. Also she's not that dishonest. ;)