Fall River school officials are investigating after two kindergarten students wandered away from a city elementary school in the middle of the day without proper winter attire. The girls were found walking in the neighborhood less than an hour after they were noticed missing Wednesday from Mary Fonseca Elementary School. They were unharmed. The sister of one of the girls noticed they were missing. Principal Teri White said in a note to parents that the children ‘‘decided to leave school’’ following lunch and even told classmates, but nobody thought to notify an adult.