The vaunted year-for-a-year is nothing more than an average increase in test scores. There is no defined "year's worth of growth;" there is no standard for a year's worth of increased knowledge.
Value-added simply looks at similarly situated students and analyzes their test scores. A child whose scores increase with the average of similarly situated students is said to have received a year's worth of growth -- a year for a year. But we are only talking the average across the state, not some educational Camelot.
Given that public education has pitiful low achievement in Ohio (and throughout the US, of course), growing with the average is not a great accomplishment at all. In fact, it's quite poor.
Of course, your local administrators will dog-and-pony these results whenever and where ever they can.
Note: As a test, review the district's remediation rates at Ohio's public colleges and universities. Regardless of the tax-funded PR, the district has a high remediation rate.