The extra rate requested is 0.2986 dollars per $100 of assessed value. Assessed value is the amount of money the City/County thinks your house and property are worth. That will likely creep up over the next 7 years - which is the length of time the extra tax would be in effect. If the school system got the referendum and it wanted it in year 8 as well, then it would have to put another referendum on the ballot in 2021.
Here's how you get a good estimate of the cost to you by using a little math and your last property tax bill.
Pull out your last property tax bill (pay 2013) and look at the long page titled "Special Message To Property Owner".
In Table 1: "Summary of Your Taxes", locate line 3. "Equals subtotal of net assessed value of property".
In the far right column of Line 3, under the heading "2013", is the important dollar value for your property that is used in this calculation.
Multiply that important dollar value by 0.003 - I used a calculator for mine. The resulting number is the extra dollars you would have to pay if the referendum is passed.
The School District hired a firm to run some sample homestead property taxes and calculate the extra dollars for variously valued residential property. Here is their results (I calculated and added the column "Percent Increase in Tax Bill"):
Home Value Extra Tax Dollars Owed Percent Increase in Tax Bill
$76,900 $50.85 7.4%
$92,500 $79.93 8.6%
$110,200 $116.65 10.4%
$175,000 $233.70 13.4%
Now, if you own homestead property larger than one acre, you will find that the extra tax you calculated is higher than shown in these examples, because the value of that extra land does not get any deductions. By following the calculation method I noted above, you'll get a better representation than by using the table supplied by the District.
Rental residential property and farmland have a property tax cap of 2%. So, increasing the tax rate by 0.3% would increase the tax bill by 15%.
Commercial and industrial property have a property tax cap of 3%. So, increasing the tax rate by 0.3% would cause an increase in those tax bills by 10%.