One of the signature policy pronouncements of President Obama’s State of the Union address was a call for states to enact laws that require students to stay in school until they either graduate or until they turn 18.

It is an idea that is widely seen as a means of adding to the long-term potential of students in terms of their likelihood to go to college and become more marketable to potential employers. Studies have pointed to the costs to taxpayers that result from young people dropping out of school. Still, it is a concept that comes with some additional consequences — and costs — that make it difficult to implement, education experts say.

With more students remaining in school until age 18, it creates a greater need for teachers and classroom space, both of which are in limited supply in most states.

“When students are not allowed to drop out, they do better,” the president said in his speech. “I am proposing that every state — every state — requires that all students stay in high school until they graduate or turn 18.”

It is far from a new or novel idea. Indeed, 20 states and the District of Columbia have requirements in place mandating that students remain in school until they reach age 18. In 18 states, the mandated age is 16 and in another 11 states the age is 17, according to the National Conference of State Legislatures (Most countries in Europe require students to attend school until age 16).

Indeed, there is considerable research showing that stronger anti-dropout laws lead to increased earnings for students over the course of their lives. A study conducted in 2003 for the National Bureau of Economic Research estimated that “dropouts compelled to take an additional year of high school earn about 10 to 14 percent more than dropouts without the additional year.”

A White House document outlining the items in the president’s speech also stated that raising compulsory school requirements “will curb the high school dropout crisis and set students down a path of academic and career success.”

Yet, raising the age requirements comes with some additional costs to the states. And in a time when state governments are having trouble with paying for the services they provide, many find the prospect of compulsory attendance until age 18 a challenging, if honorable, idea.

“When you boil it down, it’s a cost issue,” said Pedro Noguera, an urban sociologist and professor of education at New York University. “The more kids you keep in the system, the more people that have to be served. The bottom line is that, if you keep more students in school, you need more teachers, more classroom space and more money to pay for them.”

As an example, Noguera said, the state of California decided in the 1990s that it would lower the class size to 22 students per classroom.

“That created a major crisis,” he said. “It created an immediate teacher shortage, especially in the inner cities, where teachers left to work in suburban school districts that paid more. And the state wound up being unprepared for all the changes than went along with that decision.”

Opponents of the move to increase compulsory school attendance until age 18 argue that such policies interfere with the rights of parents to make their own choices for the education of their children.

Furthermore, they argue that such laws represent an intrusion of the government in the lives of individuals and that these laws ultimately fail to retain students who are already disengaged from schools and from learning. Also, they argue that these laws disrupt the classrooms, by forcing students to remain in classes against their will.

Still, many education experts contend that the benefits of increasing the age of compulsory school attendance far outweigh any potential challenges.

Noguera said that the changes in the law would have additional benefit if there were more specialized schools for students who have not fared well in traditional classrooms.

“There are kids who don’t function well in traditional schools,” he said. “And we need more schools that take into account kids who don’t come to school because their schools are not safe, particularly regarding gang violence.”

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