SUMTER, S.C. — Lexie Kinder solves problems during math class, earns gold stars from her teacher and jokes with classmates at her elementary school.

All without leaving her living room.

Born with a chronic heart disorder that weakened her immune system and made attending school risky, Lexie, 9, was tutored at her home in Sumter for years. But this spring, her family began experimenting with an alternative — a camera-and-Internet-enabled robot that swivels around the classroom and streams two-way video between her school and house.

“She immediately loved the robot,” her mother, Cristi Kinder, said, of the device, called a VGo, which Lexie controls from her home computer. Lexie dressed up the robot, which is about the height of her third-grade classmates, in pink ribbons and a tutu, and she renamed it Princess VGo.

A small but quickly growing number of chronically ill students — at least 50 across the country — now attend school virtually with what are called “remote presence robots.” The technology is still expensive (a VGo costs $6,000, in addition to $1,200 a year for maintenance and other costs) and imperfect (when the robot loses its Internet connection, it goes lifeless and must be pushed).