A few questions might help:
How many pages in each yearbook?
How many yearbooks total?
How heavy do you want the cover stock?
What ballpark budget do you have?
(i.e. it can be done with a $1500 hand bookletmaker and manual work if you have to, or it can be done with a $25000 collator/bookletmaker with ease...) If you have a local printer, you might also have them do the bookletmaking to get a nice tight product that's also trimmed square and/or have the bleeds trimmed. You could also have a local printer run the cover stock if you want a very heavy cover stock, score it, and saddle stitch it into booklets and start with printing just the interior pages yourself.
