A teacher assesses a student's report on a heated debate about curriculum…

Concept. A collective noun — board, committee, jury, team, family — names one group made up of several members, and English lets it take either a singular or a plural verb. The choice is governed by notional (sense) agreement, and it is the agreement number itself that does the signalling: singular agreement construes the group as one undivided unit, while plural agreement construes it as its separate members, acting, thinking or feeling individually. Both agreements are grammatical; each one carries a different construal of the same noun.

Application. The question does not ask which sentence could be written about a split board — it asks which verb form indicates internal disagreement. That points at the grammatical device, and the device is plural agreement, which is what presents the members as individuals rather than as one body. The debate is reported as already finished, so the form must also be past tense. The past-tense plural of be meets both requirements at once: The board were divided over the curriculum changes.

Contrast with the other forms.

• "Is" — present tense, singular agreement. The present tense does not fit a debate reported as finished, and the singular agreement construes the board as a single body rather than as its individual members.

• "Was" — past tense, singular agreement. The time frame fits, and the form is entirely grammatical after a collective noun: the board was divided is standard English, and American usage often prefers it. But there the disagreement is carried by the surrounding words, in particular the participle divided; the singular verb form itself construes the board as one unit, so it is not the form that marks the members as holding separate views.

• "Has" — present tense, singular agreement, and a form of have rather than be. It is an auxiliary awaiting a past participle, so on its own it cannot express the state being reported.

• "Were" — past tense, plural agreement. It matches the past time frame, and its plural agreement is the grammatical marker that presents the board as its separate members, which is exactly what the question asks the form to indicate.

Cross-check. The pronoun test makes the construal audible: the board were divided in their views is natural, while the board was divided in their views pairs a singular verb with a plural pronoun. Style authorities put the rule the same way — MLA states that a collective noun takes a plural verb "when the individuals composing the entity act individually", and gives The team are in disagreement as its own example.

A note on usage. Collective-noun agreement is a genuinely two-way area: British usage takes the plural readily, American usage leans to the singular, and Cambridge and Oxford both record either verb as permissible with board. What settles this item is the narrower question actually asked — which form indicates internal disagreement — and on that the authorities agree that plural agreement is the marker of members taken individually.

Answer: Were.