How well-known is the expression 杯弓蛇影? I like this 成语 and brought it up in a conversation, but the person I was speaking with (an expat Chinese) didn't know it. So I would like to know how well-known it is. Would a 10 year old in Beijing be likely to know it, for instance? Or, a primary school teacher, or a 20 year old science student?
In my mind, most well-educated individuals in China know the meaning of '杯弓蛇影' ，at least they heard about it (even do not fully understand the meaning.) 

'杯弓蛇影' appears in our textbook of elementary school.