I see your point. However, while it may have existed a long time, there is a constant turnover of 'faces'. In many older neighborhoods, as the owners die off, young couples typically move in.
I admit the Eureka concept is a bit far-fetched.
But... what if all it took was 30 or 40 couples with children who would be a part of a test ?
Would people in our government go that far ? Is doing that possible ?
The idea is too ludicrous to even consider. Why would anyone even bother to try to hire actors or plant agents as families and children? You’d accomplish the same goal if you just sent some guy into any school to go on a rampage. In fact, your plan would be much more likely to succeed.
So why would anyone pursue an over-complicated conspiracy that just involves more people who could talk, or make mistakes, and who would have to be paid very well, when you could just do it with one guy?