The objectives of the study were: (1) To develop and standardize environmental science achievement test. (2) To compare the mean achievement scores of two groups of students to be taught environmental science with mastery learning and conventional methods before and after the experimental treatment. (3) To compare the mean self-concept scores of two groups of students to be taught environmental science with mastery learning and conventional method before and after the experimental treatment. (4) To compare the mean classroom trust behaviour scores of two groups of students to be taught environmental science with mastery learning model and conventional method before and after the experimental treatment. 

The hypotheses of study were: (1) At the end of experimental treatment, the group of students taught environmental science through mastery learning will score significantly higher on the criterion achievement test than the group of students taught through conventional method. (2) At the end of experimental treatment, the group of students taught environmental science through mastery learning will attain significantly higher mean score on self-concept questionnaire than the group of students taught through conventional method.  (3) At the end of experimental treatment, the group of students taught environmental science through mastery learning will attain significantly higher mean score on the classroom trust behaviour scale than the group of students taught through conventional method. 

The sample comprised 117 students of Class V from Marigold Public School, Noida.

Children Self Concept Scale by Ahluwalia, Classroom Trust Behaviour Scale by Pareek et al., Hindi Edition of Non-Verbal Culture Fair Intelligence Test by Rao & Singh, Socio-economic Status Scale (Urban) by Kohli, and Environmental Science Achievement Test (Test-retest coefficient= 0.76) developed by researcher were used for data collection.

Pretest–Posttest Control Design was used in this study. Experimental Group was taught through Mastery Learning whereas Control Group was taught through Conventional Method. The duration of Treatment was 12 weeks.

The findings of the study were: (1) There is significant difference in the academic achievement of students taught by mastery learning strategy and conventional method of teaching. (2) Mean achievement score of experimental group is higher as compared the mean achievement score of control group. (3) There is significant difference in the mean gain scores of experimental group and control group. Experimental group scored higher as compared to the Control group. (4) There is significant difference between the experimental and control groups on the variable of self–concept. The students of experimental group scored more on self-concept questionnaire as compared to students of control group. (5) There is significant difference in the classroom trust behaviour of students taught through mastery learning strategy and those taught by conventional method of teaching. (6) There is significant difference in the mean gain classroom trust behaviour score of experimental group and control group. The students of experimental group scored higher mean gain score as compared to students of control group.