The most likely cause of the problem with the original field coding is that is unnecessarily nests some of the fields. Doing so may result in Word evaluating some of them mathematically. You also don't need the MERGEFORMAT switch. Thus:
{IF{ { MERGEFIELD School_address } }<> {REF Key \* MERGEFORMAT } "{IF{MERGESEQ}> 1 {QUOTE 12}"} { SET Key { { { MERGEFIELD School_address } } } }
should only be:
{IF{MERGEFIELD School_address}<> {REF Key} "{IF{MERGESEQ}> 1 {QUOTE 12}"} {SET Key {MERGEFIELD School_address}}

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]