When voters in the Napoleon school district turned-down a property tax on the November ballot last fall by over 700 votes; the school board had to look at other options.    The board took action during their Monday meeting this week by approving a resolution to place a half-percent earned income tax on the ballot in the May primary election this year.   An earned income tax  would only generate revenue from wage earners; and not from Napoleon school district residents that are on fixed incomes like pensions, social security, unemployment or interest income.   This income tax increase is proposed for a five year period; and is estimated to produce about 1.1 million dollars in revenue for Napoleon school operations.    Even if this level of income tax passes; the Napoleon board would still have to make more cuts in expenses, to balance their budget.     The Napoleon school board also considered a three-quarter percent income tax hike; but decided to go with the smaller amount in May.