I've always hated study island with a BURNING passion. I've finally decided to write my review.
I'm going to cut down on personal experience and tell you what you want to know. Why do people hate it?
For me, science and history are fairly simple and easy, with the lessons. There are some broken questions here and there with false facts, but it goes away after a while.
HOWEVER,
Math and ELA are very hard for me, the lessons are impossible to track down what you want to use. ELA is somewhat okay, but math?
I cannot say ANYTHING good about Math. The teachers have to use calculators! Professionals resorted to using an external object. That's right, it IS that hard.
It's usually confusing and nearly impossible.
The game modes are poorly scripted and barely work, if they DO work, that is.
You're honestly better of using IXL.
TL; DR; Math bad, game bad, use IXL.
P.S. I made this account for the sole purpose of writing this review.
Edit: I forgot to mention, this site induces heavy stress upon the user most of the time, who wants that?