CHICAGO — The mother of an elementary school student who took a gun to school in a backpack — which “accidentally discharged in the backpack while inside a classroom,” and grazed another student in the stomach — has been charged and will appear in court Wednesday, Chicago police said. Tatanina Kelly, 28, faces three misdemeanor counts of causing a child to be endangered, said Kellie Bartoli, a police spokeswoman. Kelly is due to appear in court later Wednesday. The charges stem from an accidental shooting Tuesday morning at Disney Magnet School in Buena Park. A student at the school in the 410…