The research aimed to investigate the effectiveness of a proposed NGSS aligned science curriculum in the development of explanatory models of scientific phenomena to elementary students. 
The research sample consisted of 40 first grade male and female students at Umm El Moameneen Primary Mixed School, East Nasr City Educational administration, Cairo Governorate.
The researcher used the quasi-experimental approach based on one-group pre-test–post-test design, in teaching the “Forms of Energy" unit of the proposed curriculum by applying the research tool, “the scale of explanatory models of scientific phenomena".
(Researcher's Development)
The findings concluded that the proposed NGSS aligned science curriculum is effective in the development of explanatory models of scientific phenomena to elementary students. The effect size of the “Forms of Energy" unit of NGSS aligned science curriculum in the development of explanatory models, as a whole, is (29.29) 
In light of these findings, the researcher recommended developing and building science curricula at the K-12 grades (Pre-university level) in Egypt, based on NGSS dimensions, i.e., Scientific and Engineering Practices, Crosscutting Concepts and Disciplinary Core Ideas of science curricula at K-12 grades (pre-university level) in Egypt.