An investigation of the effects of the Building Blocks prekindergarten mathematics curriculum on the oral language and letter recognition of children, with additional analyses of the moderating role of children's gender and ethnic group on those effects, as well as the mediating role of the classroom and teaching environment on the relationship between children's treatment group assignment and mathematics achievement, based on data from 1,305 children in 105 classrooms who participated in the Scaling-up TRIAD: Teaching Early Mathematics for Understanding with Trajectories and Technologies, a large-scale cluster randomized trial