My brother attended North Star Camp in Hayward, Wisconsin.  I attended Camp Nokomis (homesick-went home after 2 weeks) also in Wisconsin and like Jenny Schwartzburg who responded above, I spent 3 summers at Harand Camp.  While I don't think Harand was specified "Jewish" because I remember some in my cabin not being Jewish, they did sing the Lord's Prayer at Friday night assembly.  I don't remember if it was called actual "services."

Bonnie Gould
Rsearching:
Perlin/ Peker/ Pekier from Belarus
Rabinovitz from Ruzhin, Ukraine
Siegel from Riga, Latvia and Taurage, Lithuania
Hemanow/Heiman from Riga Latvia