State lawmakers sent new graduation requirements to Gov. Jennifer Granholm last week that will make the state's high school standards among the toughest in the nation. Schools are already rethinking schedules and electives - and adding up the costs - of providing a more rigorous curriculum. There is particular concern in cash-strapped districts such as the Detroit Public Schools, which plans to offer signing bonuses to attract math and science teachers as well as foreign language instructors. "For a district that is chronically short mathematics and science teachers, it may be a huge hurdle for them," said Michael Addonizio, professor of school finance at Wayne State .