While her husband and Mexican President Felipe Calderon fielded reporter questions on immigration at the White House, an unsuspecting Michelle Obama was prodded on policy by an unlikely source... a second grader.

Mrs. Obama appeared at the New Hampshire Estates Elementary School in Silver Spring, Maryland with Mexico's first lady Margarita Zavala.  The two were there to participate in a physical education class with students and visit with them during their lunch hour. 

But after several gym activities in which the first ladies merrily skipped and hopped with students, things got serious when a young girl in the class brought up immigration policy during a brief question and answer session with Mrs. Obama and Mrs. Zavala.

The student told Mrs. Obama that her mother said the president was trying to put away everyone who did not have papers, apparently referring to the recently-signed Arizona law that allows law enforcement officials to detain anyone suspected of being in the country illegally and requires individuals to carry proof of citizenship or valid immigration documents.

It is unclear what prompted the child's comment, but Mrs. Obama responded immediately without hesitation. 

"That's something that we have to work on, right? To make sure that people can be here with the right kind of papers," the first lady said as other students looked on with bemusement. "We have to work on that. We have to fix that. Everybody's got to work together in Congress to make sure that happens."

The Obamas are hosting Mexico's first couple for an official state dinner Wednesday evening, just three weeks after Arizona's Republican Governor Jan Brewer signed the state's controversial immigration bill into law. 

The legislation, which takes effect next month, has sparked a nation-wide backlash from critics who argue that it encourages racial profiling.

President Calderon characterized the legislation as "partial and discriminatory."

"We will retain our firm rejection to criminalize migration so that people that work and provide things to this nation will be treated as criminals," he told reporters in the Rose Garden. 

Texas Republican Congressman Lamar Smith sent a letter to Secretary of State Hillary Clinton Wednesday urging her to request that Mexican officials avoid interfering in U.S. immigration policy.

"President Calderon and other officials of the Mexican government have crossed the line," Smith said in a statement.  "It is well recognized in international law that immigration controls are an internal matter, and not subject to international scrutiny.  Yet, President Calderon has opposed the recently enacted Arizona immigration law, which in fact mirrors federal law."

President Obama told reporters attending Wednesday's press conference that he sees the potential for having a nation of immigrants and a nation of laws. 

The president said he told his Mexican counterpart that the U.S. has a right to secure its borders and decide who is allowed in the country, but implied that the White House will not ignore the desires of those individuals to come to America for a better life.

"We can't just try to use force to prevent that," Mr. Obama said. "On the other hand, the United States has to be able to make determinations about who comes in and who comes out in an orderly fashion."