The chief supporter and architect of school tax credits in Arizona says he's now willing to consider capping the amount of money corporations can give to support private school attendance. The "Arizona Capital Times" says Senate President Steve Yarbrough actually increased the amount corporations can give to organizations providing private school scholarships by 20 percent. But the amount has since swelled to in excess of 74 million dollars with no end in sight, which critics say is unsustainable. They also say the practice robs the state of much needed tax revenue.