A large new study, released Monday, shows that it has not been because these children had more impressive grades on average or took harder classes. They tended to have higher SAT scores and finely honed résumés, and applied at a higher rate — but they were overrepresented even after accounting for those things. For applicants with the same SAT or ACT score, children from families in the top 1 percent were 34 percent more likely to be admitted than the average applicant, and those from the top 0.1 percent were more than twice as likely to get in.