Now that school is back in full swing, kids (and their parents) may need some serious homework help. On Saturday at the Seward Park Library, volunteer high school students tutor children in math. From 2 to 3 p.m., help is offered for kindergarten through third grade, and from 3 to 4 p.m., students in fourth through eighth grades can seek assistance. Space is limited, so advance registration is required. Free. (212) 477-6770.