Assessment of NGSS-oriented lesson plans was developed in two stages. The average assessment was made by expert lecturers and science teachers in the first stage and had a score of 3.65 with fairly to very good criteria. This score was sufficient to declare the developed lesson plan worth using (> 3.0), but revisions are required to perfect it. The developed lesson plan can be reassessed by the validator through a second stage assessment with revisions such as 1) learning objectives must be in accordance with the learning will be studied at that time, 2) instructional media used must be explicitly listed, 3) elements of skills to be achieved during the learning process had not appeared in learning objectives, 4) the NGSS framework must be subject-appropriate. The revised lesson plan was returned to the validator and science teacher for reassessment. The second stage validation result obtained a score of 3.82 which was very good. The results of the lesson plan assessment at this stage have shown that the NGSS-oriented lesson plan is suitable for use in science learning