UNDATED  (AP) - The number of students attending charter schools has soared to more than 2 million as states pass laws lifting caps and encouraging their expansion.

The National Alliance for Public Charter Schools released new figures Wednesday showing a 13 percent growth in enrollment. That's the equivalent of about 200,000 students. More than 500 new charter schools opened for the 2011-12 school year.

The organization and others site the Obama administration's Race to the Top competition, new state laws and increased parental awareness about public school options as some of the key reasons for the growth.

Overall, about 4.5 percent of all public school students now attend a charter.

Charter schools are publicly funded but have more independence from many laws and regulations than traditional public schools.

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