WASHINGTON, April 16 — The commission investigating the 9/11 attacks has concluded that immigration policies promoted as essential to keeping the country safe from future attacks have been largely ineffective, producing little, if any, information leading to the identification or apprehension of terrorists. The commission said one program had proved so fruitless that it was discontinued after less than a year. The critical assessment was released this week as part of a preliminary finding to a final report due in July. It returned a spotlight to programs that have been controversial from the start, aimed mostly at people, like the...