How does a school system hire an illegal alien?

It has been discovered by ICE that the Superintendent of Schools in Des Moines. Iowa was an illegal alien. I was hired as an administrator in a local school system. I had to undergo a thorough background check. The state has an agency that does the background check and they charge the town over $5000 to do the background check.

Why did this guy fall through the cracks?

Updates
8 mo
It turns out that this guy does not have a PhD ot an Masters degree. His undergrad degree was from MIT. MIT says they never heard of him. He listed on his resume a big award that he got from a college. The college never heard of him and they never heard of the award.
How does a school system hire an illegal alien?
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