If you're going to correct somebody's grammar, it would behoove you to research the singular form of the noun first, then find the rules defining its use in the plural form. You skipped right to the plural use, and as such, have made a grievous error. My friend Mike is quite correct in his use of "staffs" for the plural, and as a musician I can tell you that while "staves" is fine when talking about multiple lines of music, you wouldn't refer to your employees in different buildings as your "staves." You'd sound like a moron. A full explanation below (the item in question is #6, the plural is directly below):
staff1 [staf, stahf] Show IPA
noun, plural staffs for 1–5, 9; staves [steyvz] Show IPA or staffs for 6–8, 10, 11.
1. a group of persons, as employees, charged with carrying out the work of an establishment or executing some undertaking.
2. a group of assistants to a manager, superintendent, or executive.
3. a member of a staff.
4. Military .
a. a body of officers without command authority, appointed to assist a commanding officer.
b. the parts of any army concerned with administrative matters, planning, etc., rather than with actual participation in combat.
5. those members of an organization serving only in an auxiliary or advisory capacity on a given project. Compare line1 ( def 38 ) .
6. a stick, pole, or rod for aid in walking or climbing, for use as a weapon, etc.
7. a rod or wand serving as a symbol of office or authority, as a crozier, baton, truncheon, or mace.
8. a pole on which a flag is hung or displayed.
9. something that supports or sustains.
10. Also, stave. Music. a set of horizontal lines, now five in number, with the corresponding four spaces between them, on which music is written.
11. Archaic. the shaft of a spear, lance, etc.