Throughout the nation"s more than 15,000 school districts, widely differing approaches to teaching science and math have emerged. Though there can be strength in diversity, a new international ysis suggests that this variability has instead contributed to lackluster (平淡的) achievement scores by U.S. children relative to their peers in other developed countries. Indeed, concludes William H. Schmidt of Michigan State University, who led the new ysis, "no single intellectually coherent vision dominates U.S. educational practice in math or science. " The reason, he said, "is because the system is deeply and fundamentally flawed. " The new ysis, released this week by the National Science Foundation in Arlington, Va., is based on data collected from about 50 nations as part of the Third International Mathematics and Science Study. Not only do approaches to teaching science and math vary among individual U. S. communities, the report finds, but there appears to be little strategic focus within a school district"s curricula, its textbooks, or its teachers" activities. This contrasts sharply with the coordinated national programs of most other countries. On average, U.S. students study more topics within science and math than their international counterparts do. This creates an educational environment that "is a mile wide and an inch deep," Schmidt notes. For instance, eighth graders in the United States cover about 33 topics in math versus just 19 in Japan. Among science courses, the international gap is even wider. U.S. curricula for this age level resemble those of a small group of countries including Australia, Thailand, Iceland, and Bulgaria. Schmidt asks whether the United States wants to be classed with these nations, whose educational systems "share our pattern of splintered (支离破碎 的) visions" but which are not economic leaders. The new report "couldn"t come at a better time", says Gerald Wheeler, executive director of the National Science Teachers Association in Arlington. "The new National Science Education Standards provide that focused vision," including the call "to do less, but in greater depth". Implementing the new science standards and their math counterparts will be the challenge, he and Schmidt agree, because the decentralized responsibility for education in the United States requires that any reforms be tailored and instituted one community at a time. In fact, Schmidt argues, reforms such as these proposed national standards "face an almost impossible task, because even though they are intellectually coherent, each becomes only one more voice in the babble (嘈杂声). " (411 words) By saying that the U.S. educational environment is "a mile wide and an inch deep" (Lines 2~3, Para. 5), the author means U.S. educational practice______.