THE BRONX - Some fourth- and fifth-graders from The Bronx are getting to trade in traditional textbooks for new laptops.St. Mary's School is one of two Bronx Catholic schools where math students are taking part in a new digital pilot program. The teacher comes up with lesson plans and guides students using an online "smartboard." Students don't get to take the laptops home, but can log in to the program from their own computers. St. Mary's principal says the school plans to expand the program to the third grade next year, and to also include English courses.