Thank you all for your testimonies, especially @anon22855873 !
Actually the sensations had faded the next morning. So they clearly needed to work on it more. Turns out they also didn’t grasp completely fields I thought they knew (I guess I wrongly phrased my questions when asking them about it). So now we’re back to looping school (and I now ask them their estimated percentage of learning completion, it seems to work fine).