I host our local homeschool community for ICAS - I invite entries and then supervise them in my home (I'm registered teacher). I have to have my own kids do them under someone else's supervision for their scores to be counted though, which WAS fine, because another homeschool mum was also a registered teacher so we supervised together and she did my kids and I did hers. Unfortunately she has moved on and no other homeschooling parents have answered my plea, so this year I will be supervising other people's children while they do it, and sending my own kids to a school with their papers to do theirs (the school is where a friend works, so they're good with that). It's worth it for us to do the supervision properly though, because both kids have won multiple medals so far, and I'd hate for them to have them invalidated because the supervision wasn't done properly.
Both of mine do them a year ahead of their level if they were at school - DD because she is on the cut off anyway, and going younger doesn't make sense for her and DS because I entered him for the experience a year too young, intending to do that level again "properly" the next year but he medalled, so we couldn't really repeat! It's not even remotely close to the level either of them are actually working at, but there is still enough to challenge them, and it's GREAT for showing them that "check your work" isn't just something I say because I feel like it, lol! Silly mistakes have cost DS at least two medals, possibly another one or two - and I'm talking mistakes he recognised as soon as he looked at the paper.