Sorry to disagree, but building a public school is a public good and therefor a legitimate use of eminent domain.
However, a Wal-Mart is not.
Let's make these disctintions clear.
The fact that they are replacing a private school is a problem, but one that's solved in other ways.
How about we recognize that when others, like the folks who put in the private school, are wise, plan ahead and generate value from their choices and decisions, it is not a legitimate function of government to point a gun at the wise party in order to steal their assets. The school first there is the school that has a right to be there.