* I’m confused. Jill Leovy reported in “Latest U.S. Export: Education for the Masses” (Feb. 20) that there has been “an enormous baby boom in Mexico during recent decades.” Agustin Gurza, however, reports that “Mexicans have slashed their growth rate in half since the 1960s” (Feb. 20). Am I missing an important point? Whoever is right, Mexico would definitely be better served by limiting the birthrate, particularly in light of the latest scientific information on global warming and the endless environmental difficulties we face.