I mean, I sometimes help my kids in very similar way. But, I find it very wrong to judge kids who were truly independent or make such projects into competition between the kids. Because the real competition is here in fact in between adults. Parent knowing that "different locations around the house to increase the probability of getting a few decent crystals" is what makes the difference. Parent who makes sure the kid takes 10 containers is what makes difference. As you said, it is not within average kid going by school education to figure it out.

> The trouble is that no one else was able or cared to do it so fast, so the deadline has been slipping for a couple weeks now, with our best crystals going to school and back a few times, getting scratches and broken bits instead of nicely growing undisturbed. A bit discouraging.

The thing is, the "no one cared" is very unlikely. Those other kids did cared. But they were doing the project as kids do - loosing attention or doing it ineffectively. Forgetting and trying re-over. Having it at bad place and thus having it grow slowly etc. And all that is part of actual doing-projects learning. It is not bad pedagogy to have kids deal with these issues and have them slowly to figure it out. It is bad to then expect the similar result as your daughters had, when the most important decision making was done by you. Or judge those kids as "dont cared".

And this is an actual issue - a kid doing the project the way that is age appropriate and in fact independent ends up labeled as not caring kid. And I think there is value in kids figuring stuff out truly independently.