Borrowing a page from New York's senior senator's weekend playbook, the mayor on Saturday announced the DOE's intention to transform four languishing Catholic schools into New York City charter schools. The plan, endorsed by the mayor and Bishop Nicholas DiMarzio, appears to be a great potential match: With underused buildings (and famously dwindling finances), the Catholic schools can offer the city much-needed facilities and classroom space. (The plan would permit the extant schools to offer 100 new seats.) But caution is surely warranted as well: The sorry physical state of many parochial school buildings (some have been used to incubate new schools since 2002) will require significant capital investment. And whether the charters will continue or extend the academic work of the Catholic schools they replace deserves close scrutiny: At least one charter school in Brooklyn, which began as a private school for a once-vibrant Greek community, was able to sustain the core of its original curriculum, thanks to the infusion of state funds. It's election season, of course, and bridge-building makes a campaign sing. But this effort is a pilot program, meant to test the waters ahead of other possible parochial-to-public-charter conversions. In a time when the city's established public schools are threatened with cuts of every stripe, does an investment in new charters, with the support and endorsement of the Church, make good economic sense?