句子分析 关于 介词+whom的句子

对于。。。来说for a group of high-school students,practising their music in someone's house is the first step to fame

for whom 修饰的是a group of high-school students，要加for的原因是：
practising their music in someone's house is the first step to fame for the group of high-school students. 这里的for是“对于谁来说”意思，整句的意思是：他们可能从作为一群大学生开始，对他们来说，在某人家里练习音乐是成名的第一步。