Let's transition from thinking about time-on-learning to considering how best to develop your own curriculum. Designing good curriculum requires a relatively simple process, illustrated below:
Curriculum development should progress from initial ideation to a formatting and drafting period, moving then to testing, reviewing and revising materials, and finally to professional development training on how to use the materials.
Let's start with ideation. What exactly is involved in this process? In other words, how to we translate initial ideas into a curriculum that fully supports the Next Generation Science Standards?
Ideation should include three different areas: scope and sequence, crosscutting concepts, and the science and engineering practices.
What are the ideas? The ideas dictate how a classroom is going to bridge the gap between the standards and curriculum, because the role of curriculum is to develop mastery of the expectations of the standards. Ideation is basically envisioning that bridge. Out of this comes scope and sequence. This is how the crosscutting concepts come alive, connect one performance expectation to the next and one dimension to the next. Questions to ask include "How are crosscutting concepts going to connect to the disciplinary core ideas?" and "How are students going to engage in the science and engineering practices required for mastery?"
Make no mistake, this is a big fish to fry. When you engage in ideation, you have to think grade-specific and you have to think September through June. That means curriculum needs to be designed in both a vertical and a horizontal fashion, nurturing students through the year and from year to year. All of this thinking needs to happen in the initial phase of ideation.
Formatting and drafting requires unpacking the performance expectations and putting them all together using the tools of curriculum: defining content, setting objects, planning lessons, choosing non-fiction reading and so on.
The second phase of formatting and drafting, which defines the context of the inquiry environment. This is where each performance expectation, each standard, is unpacked and connected. To do so, we must take into account the 12 tools listed above.
This is a lot to grapple with. You not only have to ensure that the curriculum you use addresses the standards, but ensure that general classroom teachers are supported in maintaining a rigorous curriculum and aren't limited in their own understanding. This is true even with content specialists. Just because a teacher has taught earth science every year for 10 years doesn't mean they will be comfortable with and ready to teach heredity and evolution or DNA and genetics, and so on and so forth. In some districts, designing curriculum that ensures that teachers are supported in this fashion is feasible; in others, building a 5- to 10-person team to design curriculum over the course of several years is less realistic, and in that case, thinking about purchasing NGSS-aligned curriculum is a better bet.
From here, we progress to drafting mastery objectives, the teacher's lesson objectives and creating or sourcing nonfiction reading. What you're going to find is that there's really not sufficient nonfiction reading out there for the breadth of topics covered by NGSS performance expectations. It is being developed commercially, so that presents one option; the other is to design it yourself.
Most likely you will find the same to be true of both lesson visuals and the hands-on materials required to engage in the lessons. More and more these days, districts are returning to hands-on instruction in these full inquiry environments, which is a good thing but brings in an extra element (as compared to electronic resources and apps, which have become popular in recent years). As a district or a classroom teacher, you are now faced with ensuring those materials are there.
And now onto teacher's lesson guidance. Since you're going to be faced with veteran and newcomer teachers alike, it is important to structure lessons in such a way that sufficient guidance is provided at all levels, creating a high quality of instruction. To accomplish this, teachers will need exemplars of student work, both ideal and more realistic representations, showing various strengths but not perfection. Lastly, embedded assessments and rubrics, answer keys, concept maps and differentiated instruction will all play roles.