More than a third of tweens and young teenagers in the United States said they are using smartphones to do homework, according to a survey released on Wednesday, with Hispanic students using them at a higher rate than African-Americans or whites.

"These middle school students are using mobile devices for more than entertainment purposes," said Kristi Sarmiento, research director at TRU, in an interview. "They have grown up with this technology."

Smartphones were used at home for schoolwork by 39 percent of 11 to 14 year olds, 31 percent of those surveyed said they did assignments on a tablet while nearly 65 percent used laptops, the poll by research firm TRU, which specializes in data on tweens, teens and twenty-somethings, showed.

TRU is owned by WPP Plc, the world's largest advertising group.

But usage was lower in schools, where only 31 percent of students said they used a laptop, 18 percent worked on a tablet and 6 percent used a smartphone.

The national online poll of 1,000 students showed that smartphone usage increased with age, rising from 42 percent for sixth graders to 57 percent for eighth graders.

Not all U.S. schools allow students to use mobile devices but in those that did, more than three quarters of students said the school provided the laptop and 55 percent used school tablets.

Smartphones were used by 49 percent of Hispanics surveyed, 42 percent of African-Americans and 36 percent of whites, while tablets were used by 38 percent of Hispanics, 30 percent of African-Americans and 31 percent of whites.

Laptops were used by 68 percent of Hispanics, 64 percent of African-Americans and 62 percent of whites.

Sarmiento said students questioned in the poll, commissioned by Verizon Foundation, the philanthropic arm of Verizon Communications which supports research into the use of technology, said they were excited about using mobile devices, which they said helped them to learn math and sciences better.

(Reporting by Patricia Reaney; Editing by Phil Berlowitz)

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