When i went to 8th grade (in Sweden) we did an experiment in chemistry class where we would put a tiny bit of Sodium into a bowl of water to see it fizzle about (reacting with the water), all students where allowed to carry out this on our own. However a group of student (unaware of the possible consequences) took a chunk of sodium and put it in the water, violent reaction of course which left mark in the ceiling and glass everywhere. Nothing came out of this other than quite a long talk about dangers in chemistry and so on.