P.S.- they are not required to have 100% mastery to move on. I've found them quite flexible. They moved up DD8 in math simply because I told them to. And they should do what I tell them to, I'm paying them.
They get a score card for completing a computer worksheet and obtaining 70%. They get more, the highter the percentage.
My kid better not be getting 100% all the time, I'm paying for learning not review work. They get that for 6 1/2 hours at school as my DD likes to remind me.