We use the Iowa test. I don't share the scores with them. It's a frame of reference for me and a good learning experience for them. So far, most of the time, I can predict their scores within 10 percent.
The kids have taken it both having it administered individually and in group settings. I've seen the plusses and minuses of both. In past years, my friend and I swap kids so she administers the test for my kids and I administer for hers. One time, when she was supposed to administor for my son, she went out instead and had her mother, who lives with her, do it instead. What a flipping disaster. Her mom had no idea what she was supposed to do. She put him in a hot, stuffy bedroom with a couple pencils and the test, set the timer and shut the door. Even worse, it was right before lunch, so he was hungry and sleepy. Needless to say my 60.00 was wasted.
Since moving to NJ, I've participated in Iowa testing with our homeschool group because they needed a proctor and I am qualified to do that. Most of the kids were adequately prepared for a test taking situation, but definitely not all. It pained me to not be allowed to direct certain kids in helpful but not compromising ways. For instance, I could tell that my friend's son forgot that he should skip the problem he was spending too much time on and come back to it later. I also witnessed that some of the administrators were either undertrained for their task or indifferent to it and it impacted certain kids.