My business reported all assets to the county assessor at the depreciated net book value at year end. These were ignored and a different schedule was used, increasing the values. Is this legal?

The assessor is mandated to use class life and established depreciation schedules. The net book value you calculated is for federal income tax. The assessor is not allowed to use your net book value, but the assessor should use your acquisition cost and date of acquisition to recalculate the value for property tax purposes.