was thinking about NCSY too. But. My frame of reference re NCSY is well over 20 years old. NCSY was geared to focused, secular or more assimilated kids, from public schools and yes, Jewish schools, maybe Solomon Schechter types.
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I grew up in Suburban Detroit. NCSY was basically a social outlet for kids who attended the local co-ed day school. There were some non-religious kids who came to the events, and one chapter was located in a Chabad schul so there was an aspect of kiruv rechokim, but it was msot definitely a secondary emphasis, as far as I recall.