The estimated increase in average residential property values announced this month by Franklin County Auditor Clarence Mingo was eye-popping to some Grandview Heights residents.

The tentative reappraisals indicated the value of homes in the Grandview Heights City School District has increased by 29.9 percent -- far more than in any other county school district.

"We weren't expecting to see that much of an increase. There hasn't really been anything like it in recent appraisals," district Treasurer Beth Collier said.

But that doesn't mean residents will see their property-tax rates increase by 30 percent, or that the district will see a windfall of additional property-tax revenue, Collier said.

"The fact is that the average tax-bill increase will only be about 4.15 percent," she said.

A resident whose property value rises by the 29.9 percent average would see the 4.15 percent increase in their tax bill, Collier said.

The actual increase in property value will vary from one property to the next and in various areas of the district, she said.

Someone who sees a 10 percent increase in their home's value likely will see their property tax bill decrease because their value was not as high as the average amount of 29.9 percent, Collier said. Some properties will see their values increase more than 29.9 percent and thus will have a higher increase in property taxes.

Some of the increase in property-tax bills will be because of the five-year, $233 million levy voters approved in May for the Franklin County Office on Aging, Collier said.

There are 2,613 residential parcels in the Grandview school district.

The current annual tax bill for each $100,000 in property value is $2,409. That amount would increase by $100 after the reappraisals due to the county levy and an increase in inside millage.

However, the revenue the school district receives from its operating levy will remain the same, Collier said.

"House Bill 920 (adopted by the state in 1976) limits inflationary growth on taxes," she said. "It means a school district will continue to receive the same amount of revenue approved by voters even if property values go up."

As a result, the effective millage collected in Grandview from the levy voters approved in 2014 -- currently standing at 5.45 mills -- "certainly will be going down next year, and with a 30 percent increase in property values, by a significant amount," Collier said.

The district will see an increase in property-tax revenue only from its share of the inside millage.

Inside millage is limited by law to 10 mills for any taxing district. The inside millage can be collected as a levy without being approved by voters.

The school district's share of the inside millage is 5 mills, Collier said.

"That's the only part of the school district's tax revenue that will be part of the 4.15 percent increase," she said.

The increased property values likely will impact the district's next operating levy, Collier said.

"With the higher property values, it will take less millage to collect the same amount of money as before," Collier said, "so that will mean a levy with a lower millage level."

Residents will receive a letter about the change in their property value in late August.

Property owners will be able to challenge their home's new value in September.

The estimates are tentative and will be finalized in November. Tax bills reflecting the new values will be mailed in December.

The property-value boost also likely would increase the district's debt capacity -- the amount of money it could borrow -- for a potential facilities project, Superintendent Andy Culp said.

As with an operating levy, it would mean a potential bond issue the district would place on the ballot in November 2018 would have a lower millage, he said.

Culp said he expects to announce a single option for addressing the district's facilities at the third community-engagement meeting, set for 6:30 p.m. Thursday, Aug. 3, at Edison Intermediate/Larson Middle School.

The initial seven options were presented during a May 1 community meeting and were narrowed down to three before a June 8 gathering.

After each of those meetings, residents, staff and students were invited to give their feedback through an exit ticket, in addition to online surveys posted on the district's website or at coffees hosted by residents.

The input received from the community is helping to shape the final recommendation Culp will present first at the Aug. 3 meeting, then formally to the school board at its Sept. 19 meeting, he said.