The Acorn BBC Micros you used at school were all 6502 based and without any coprocessor. The ARM1 coprocessor was never a commercial product (if I remember correctly). The first ARM2 processor that most of saw or used was in the Archimedes.Yes the first ARM silicon was a coprocessor for the 6502 based BBC Model B computer. I used to use one of those at school back in 1982.