I want to know the answer to the following question:
Boston police and local groups make an effort toprevent youth from doing what?
All the background I'm provided with is that "Boston's low crime rate since the 1990s has been credited to the Boston Police Department's collaboration with neighborhood groups and church parishes to prevent youths from joining gangs, as well as involvement from the United States Attorney and District Attorney's offices.". Is that enough to answer the question?