The floor grates was a big one here. The three year old boys still lay on their tummies and stare down them hoping to see the spider we saw crawl in there several months ago and has never been seen again.

Sad to say but the only reason my 18 month old stopped doing this was that she got her finger stuck in the grate and cut it - just a nik like a paper cut so it I'm sure it hurt a lot. She was not inmpressed. After that my verbal warnings had her thinking twice most of the time and while she would go and look down she rarely poked into them after that.

Putting one of the highchairs over it to make it less accessible helped a bit in the sense that it wasn't easy to get in there to play.

IF it was my own they would be getting a tap on the hands along with the stern we don't do that and especially after hours. If you find it is only being done during daycare then it is being done for your attention so you may have to keep him closer if you are going to be busy doing something.