Frede (1998) investigated commonalties and differences
among the model programs with evidence of long-term effectiveness.
The models she examined had been subject to outcome
studies at least through elementary school, provided center-based
preschool experiences for low-income children, and included in
their reports written descriptions of their curriculum and classroom
practices (see Table 4-1). Based on close analyses of these
descriptions, the following factors were found to be present in
most programs: