We are not attempting to provide a full discussion of all possible influences on science education; rather, we focus on four major components that have critical roles to play and how they will need to evolve in order to implement the kind of science education envisaged by this framework. Our discussion also does not include detailed consideration of the process of gaining support for adoption of standards—for example, developing public will and engaging with state and local policy makers. We also do not discuss informal settings for science education, which provide many opportunities for learning science that complement and extend students’ experiences in school .
A Complex System
Much of the complexity of science education systems derives from the multiple levels of control—classroom, school, school district, state, and national—across which curriculum, instruction, teacher development, and assessment operate; thus what ultimately happens in a classroom is significantly affected by decision making distributed across the levels and multiple channels of influence.
Each teacher ultimately decides how and what to teach in his or her classroom, but this decision is influenced by decisions at higher levels of the system. First, there is the effect of decisions made at the school level, which include the setting of expectations and sequences in certain content areas as well as the principal’s, department chairs’, or team leaders’ explicit and implicit signals about teaching and learning priorities . Leaders at the school level may also make decisions about the time and resources  allocated to different subjects within guidelines and requirements set by the state, teacher hiring and assignments, the usage of science labs, and, in some cases, the presence of a school building’s laboratory space in the first place. The school leaders’ expectations, priorities, and decisions establish a climate that encourages or discourages particular pedagogical approaches, collegial interactions, or inservice programs [11, 12]. Furthermore, a school’s degree of commitment to equity—to providing opportunities for all students to learn the same core content—can influence how students are scheduled into classes, which teachers are hired, how they are assigned to teach particular classes, and how instructional resources are identified and allocated [13, 14].
At the next level of the system, school districts are responsible for (1) ensuring implementation of state and federal education policies; (2) formulating additional local education policies; and (3) creating processes for selecting curricula, purchasing curriculum materials, and determining the availability of instructional resources. District leaders develop local school budgets, set instructional priorities,