But any student who has not slept in chemistry lessons, using potassium peroxide and a number of quietly conducted home reactions with completely available substances such as peroxide and a kilogram of apples, can get potassium cyanide at home.

In Soviet times and schoolchildren were more educated, and reagents were more affordable, but something was not massively poisoned with cyanide. Maximum harmless smoke stoves from analgin, etc.

And now for the video on YouTube about this smokevuh the man was conditioned with a large fine.

Something is clearly going wrong...

However, some schoolchildren and students in the past went a little further.
Read "Tales of the old chemist"