This ballot title review proceeding brought under ORS 250.085(2) concerns the Attorney General’s certified ballot title for an initiative petition that the Secretary of State has denominated as Initiative Petition 50 (2008). Initiative Petition 50, if adopted, would add a section to Article XV of the Oregon Constitution that would grant a tax credit to parents “who directly spend money for educational expenses” as defined in the proposed measure equal “to the amount of their expenses.” The amount so allowed would be “capped” (the measure’s term) at $200 per child for calendar year 2009, $400 per child for calendar year 2010, and $600 per child for each calendar year thereafter. The legislature could increase the credit, but not decrease it. The legislature also could expand the list of educational expenses, but could not shorten it.
Petitioners are electors who timely submitted written comments to the Secretary of State concerning the content of the Attorney General’s draft ballot title and who therefore are entitled to seek review in this court of the resulting certified ballot title. See ORS 250.085(2) (stating that requirement). We review the Attorney General’s certified ballot title to determine whether it substantially complies with the requirements of ORS 250.035(2)(a) to (d). ORS 250.085(5). As we shall explain, we conclude that certain of petitioners’ challenges are well taken, and we therefore refer the certified ballot title back to the Attorney General for revision. See ORS 250.085(8) (authorizing that disposition).
The proposed measure consists of eight subsections. The central provision is subsection 2, which provides, in part:
“Parents who directly spend money for educational expenses listed in [subsection 5 of] this Section shall be granted an Oregon income tax credit equal to the amount of their expenses. The tax credit shall be capped at $200 per child for calendar year 2009; $400 per child for calendar year 2010; and $600 per child for calendar year 2011 and each subsequent calendar year.”1
*478“Educational expenses” then are defined in subsection 5 as
“textbooks, transportation, activity fees, school uniforms, school activity uniforms, musical instruments, electronic devices used in a class or for homework, tuition, and registration fees.”
(Emphasis added.) It is the proposed measure’s authorization of a tax credit for tuition that lies at the heart of this case.
The Attorney General certified the following ballot title for Initiative Petition 50:
“AMENDS CONSTITUTION: PROVIDES STATE INCOME TAX CREDIT FOR EDUCATIONAL EXPENSES FOR CHILDREN ATTENDING KINDERGARTEN THROUGH HIGH SCHOOL
“RESULT OF TES’ VOTE: Tes’ vote provides state income tax credit for education expenses, including tuition, for children attending kindergarten through high school; reduces revenue available for state services.
“RESULT OF ‘NO’ VOTE: ‘No’ vote retains current law, which does not provide a state income tax credit for the educational expenses of children attending kindergarten through high school.
“SUMMARY: Amends constitution. Constitution currently contains no provisions relating to income tax credit for children’s education expenses. Measure provides state income tax credit for educational expenses for children attending kindergarten through the 12th grade, children completing high school diploma equivalency. Tax credit is amount of expenses, up to $200 per child in 2009, increases to $600 by 2011. Applies to religious, private, public schools. Legislature may increase, not decrease, amount of tax credit. Parents claiming child as dependent and emancipated children not claimed as dependents are entitled to credit. Educational expenses defined as books, transportation, activity fees, uniforms, musical instruments, tuition, registration, electronic devices. Legislature may expand but not restrict qualified expenses list. Reduces revenue for state services; provides no replacement funds. Other provisions.”
*479Petitioners challenge the Attorney General’s caption, “yes” vote result statement, and summary.
ORS 250.035(2)(a) requires that an Attorney General’s certified ballot title contain a “caption of not more than 15 words that reasonably identifies the subject matter of the state measure.”2 This court reviews a challenge to a caption to determine whether the caption “substantially compl[ies]” with that requirement. ORS 250.085(5). See also, e.g., Honeyman v. Myers, 342 Or 126, 130-33, 149 P3d 1147 (2006) (illustrating process). The caption is the cornerstone of the ballot title; it must identify the proposed measure’s subject matter in terms that will, inter alia, inform potential petition signers and voters of the sweep of the measure. See, e.g., Dale v. Myers, 328 Or 466, 469-71, 980 P2d 157 (1999) (caption required to mention payroll deductions, although such deductions never mentioned in proposed measure itself, because primary subject matter was deduction process).
In the present case, petitioners argue — and we agree — that the principal effect of the proposed measure (among other important effects) will be to allow tax credits for parochial and other private school tuition. That is true because, under the state’s present public education system, parents ordinarily do not pay tuition. Thus, although all the other expenditures listed in the measure are likely to be made by all parents, the credit for “tuition” runs in favor of the parents of children in religious and other private schools. Moreover, tuition expenditures are almost invariably the largest educational expense of parents who send their children to those kinds of institutions. Such a public policy choice — whatever its merits — would represent a very significant change in Oregon law, both by reducing the general fond by the collective total of the tax credits and by facilitating parents’ desire to enroll their children, with the aid of public tax dollars, in parochial and other private schools. Those facts make the subject matter of the measure not merely a “tax credit.” It is, instead, a tax credit aimed most specifically *480at lessening the tuition burden of those who choose to send their children to parochial or other private schools.
The Attorney General’s caption blandly refers to a “tax credit for educational expenses.” That may be accurate, but it hardly can be said to note, much less highlight, the actual major effect of the proposed measure. The caption must reflect specifically the proposed tuition offset aspect, as discussed above, if that is possible within the 15-word limit provided in ORS 250.035(2)(a). We believe that it is possible and therefore hold that the Attorney General’s certified caption fails to comply substantially with the requirements of ORS 250.035(2)(a). We must refer the ballot title to the Attorney General for revision.
Petitioners challenge the Attorney General’s “yes” result statement on the same ground that they advance respecting the caption, and we again agree that a modification is required. The “yes” result statement does mention “tuition,” but again says nothing about who benefits from a tax credit for that expenditure. The Attorney General’s certified ballot title is referred to the Attorney General for revision in that respect as well.
Finally, petitioners challenge the Attorney General’s summary, arguing that the summary must include a description of Article I, section 5, of the Oregon Constitution,3 to give prospective petition signers and voters perspective as to the policy choice they are being asked to make. We agree with the Attorney General that he was not required to include that material in his summary. We do note that, on remand, he is free to further consider the question and include that material, if he so chooses.
Ballot title referred to the Attorney General for modification.
Subsection 3 confirms what subsection 2 already states: The tax credit applies for “each child” of the taxpayer. Subsection 4 provides that “child” means *478any person under 21 who is taking classes to complete grade levels from kindergarten through the twelfth grade.
When, as here, the proposed measure would amend the Oregon Constitution, the caption may contain two additional words, viz., “amends constitution.” Those words appear in the Attorney General’s caption for Initiative Measure 50.
Article I, section 5, of the Oregon Constitution provides, in part:
“No money shall be drawn from the Treasury for the benefit of any relig[i]ous, or theological institution * *