(1) good/bad school area refers specifically to the ratings of the public elementary, middle, and highs school to which persons living at an address are assigned by geography (it's a measure of what you are entitled to as a result of living at a given address, not what happens to be nearby otherwise); starting a private school (whether a regular private school or a privately owned charter school) has no direct effect on that, regardless of its ratings.

(2) There's pretty strong evidence that school ratings mostly are a measure of the students assigned, so if you want to influence ratings of the local schools to manipulate real estate prices, you don't establish a new private school and try to make it good, you make a new private school and selectively admit low-performing students from the target area.