Background: Middle school (Grades 6-8, ages 11-14) is a cognitively critical time in which students move from concrete to formal operational thinking. Despite the explicit instructions given in the National Education Policy 2020 (NEP 2020) for competency based evaluation, there was no psychometrically standardized instrument to measure micro level thinking sub skills at the discrete level in this population in the regional context of Gujarat.

Objectives: To validate the Micro Thinking Skills Test (MTST) a diagnostic instrument in six subscales that has been constructed, developed, evaluated for validity and reliability, and normed.Objective: The Micro Thinking Skills Test (MTST) is a diagnostic instrument in six subscales that has been constructed, developed, validity and reliability tested, and normed.

Methods: The methods used were the nine phase psychometric standardization design. Lawshe's Content Validity Ratio (CVR) with a panel of 12 experts was used for expert content validation. The final item selection was determined by Classical Test Theory (CTT) item analysis. The standardization sample consisted N = 1,200 students (400 students in each grade) selected by Stratified Multi-Stage Cluster Sampling from 35 schools of the study area Anand and Kheda districts in Gujarat. Content (CVI), construct (Exploratory Factor Analysis), and criterion approaches were used to evaluate the validity. Cronbach's alpha, split-half by Spearman-Brown, and two-week test-retest coefficient were used to test for reliability.

Results: The final 72-item MTST exhibited good psychometric characteristics with high overall CVI = 0.87 (content validity), a six-factor EFA solution that explained 60.07% of the total variance, and an r = 0.61 (p < .001) KMO = 0.89 (construct validity) with teacher performance ratings (criterion validity). Internal consistency was very high (Cronbach's α = 0.93) and test-retest reliability, r = 0.87 (p < .001, n = 100, 2-week interval). Mean scores increased significantly across grades (Grade 6: M = 38.72; Grade 7: M = 42.15; Grade 8: M = 45.89; F(2,1197) = 156.84, p < .001, η² = 0.208), confirming developmental sensitivity. There were no significant differences between genders (p = .216). Percentile, stanine and t-scores for each grade were developed.

Conclusions: The MTST is psychometrically sound, meeting international standards of educational diagnostic instruments. It addresses a documented gap in the Indian assessment landscape by offering a valid, reliable and regionally normed sub-skill diagnostic assessment tool for middle school students that facilitates the implementation of the NEP 2020 competency-based assessment goals.