This paper examines the argument that school sponsorship mechanisms are, relative to significant others' influence (SOI), a more effective determinant of educational plans and attainment in societies geared toward sponsored mobility. This argument has been previously validated with respect to aspirations for higher education in Israel. The present paper analyzes the determinants of curriculum placement in Israeli high schools. In particular, it examines the relative impact of SOI versus ability grouping at the junior high level. A path analysis of longitudinal data for a representative sample of junior high students shows that their aspirations for specific high school training are determined mainly by SOI. Yet, their curriculum placement in the tenith grade is affected by ability grouping much more than by SOI or aspirations. These findings are supported by additional discriminant analyses of high school aspiration tracks and track placement. It is also found that the high school tracking of students of Oriental origin is more heavily influenced by institutional mechanisms than the tracking of their Ashkenazi counterparts. The above processes are interpreted as indicative of a transitional period in the formation of educational careers in sponsorship-oriented systems. In such systems, sponsorship mechanisms may determine educational attainment at all school levels, but their cumulative effect on aspirations is apparent only at an advanced stage of schooling. Comparative studies which may further validate this thesis are proposed.