shall reserve not more than 15 percent of the agency’s allotment under
section 6821(c)(2) of this title to award subgrants to eligible entities in the State that have experienced a significant increase, as compared to the average of the 2 preceding fiscal years, in the percentage or number of immigrant children and youth, who have enrolled, during the fiscal year for which the subgrant is made, in public and nonpublic elementary schools and secondary schools in the geographic areas under the jurisdiction of, or served by, such entities; and