Attempt of statement and the decision of a task of an estimation of efficiency of merges of two high schools with use of the greatest possible formalization is done. As effects from merges of high schools the degree of approach the purposes of development of high schools is accepted. As the purposes criteria of a world rating of high schools, and also the purposes connected to mission of any high school are accepted. Results on sizes of relative effects or damages from merges of high schools in dependence as from a degree of development of high schools, and their scale are received.