That may well be the same number of nonregistered sex offenders as other areas. It just means these ones were caught + charged + convicted + jailed + lost earning capacity thus landed in a cheaper area. Offenders in better circumstances would have had different outcomes. So, I would say assume that many offenders anywhere and parent accordingly.
The terrible schools concern me more. What tells you that the schools are this awful?
In most cases, homeschooling has the cost of at least one parent staying home. Private school costs are obvious, too. So, if you'd be taking one of these tacks *only* because the local school is awful, the house isn't really offering savings.
If you're committed to homeschooling for other reasons, the cost is the same regardless of the home's location. But homeschooling, you'll still want to be in a healthy community with healthy programs and healthy neighbours available to your kids, so this one might fail in terms of that workaround idea.
If the other viable option is to move in three years, then you're usually advised not to buy, just on the buying/selling/moving costs alone (not to mention the stress of big changes, loss of community, etc).