President Barack Obama's call for every state to require school attendance until age 18 may spark a flurry of action in some statehouses, but changing attendance laws will do little by itself to drive down the nation's dropout rates, experts on the issue say. In his State of the Union address last month, President Obama said states should require that "all students stay in high school until they graduate or turn 18," and said that when students aren't allowed to drop out, "they do better." Twenty-one states and the District of Columbia already require students to remain enrolled until they are 18 years old, while 11 others require attendance until age 17, according to the Denver-based Education Commission of the States. The other 18 states still use the traditional age of 16 as their attendance requirement, though lawmakers in several of those states have tried unsuccessfully in recent years to raise it. While bumping up the compulsory-attendance age in state laws sends a strong message to students and parents about the obligation to remain in school, experts and educators alike say that states and districts won't make much of a dent in their dropout problem without comprehensive strategies for making school engaging and relevant and for spotting and addressing early signs of dropping out. Whether President Obama's exhortation to states will gain any traction remains to be seen. Setting school attendance requirements has traditionally been the purview of states and local districts, and many efforts have run into fierce opposition to budging from an attendance age of 16. A major reason is cost and issues around local control of schools.