I remember at Primary School, there was an organisation close to the village called the Closed Brethren (we used to call them the Happy Clappers!). Anyone remember them? In any case, me and the 3 of them used to sit out of the assemblies, but they never used to really associate with me much - I was an unbeliever!
Personally I used to quite enjoy getting out of the Assemblies as I could always read books, and in later years at Secondary School I used to finish off homework I hadn't done.
All in all, the getting out of assemblies part was the only decent thing about the whole arrangement. Oh, except one year when an elderly assistant got my to decorate the Christmas tree for her when I was sitting outside of an assembly. I was about 6 so didn't know what was wrong with it, except my mam went apesh**t! I still find it funny to this day...