The applicability of the Establishment Clause to public funding of benefits to religious schools was settled in Everson v. Board of Ed. of Ewing, which inaugurated the modern era of establishment doctrine.
The Court's majority holds that the Establishment Clause is no bar to Ohio's payment of tuition at private religious elementary and middle schools under a scheme that systematically provides tax money to support the schools' religious missions.
Legislatures not driven to desperation by the problems of public education may be able to see the threat in vouchers negotiable in sectarian schools.
I retired when the Supreme Court rose for the summer recess in 2009, and a couple of weeks later I drove north from Washington with no regrets about the prior 19 years or about the decision to try living a more normal life for whatever time might remain.
In a perfect world, I would never give another speech, address, talk, lecture or whatever as long as I live.
It may be that the seemingly intrinsic attraction that past time has for me is merely a desire for escapism, as I look out at the nation and world with little optimism.