Traditional secondary physics assessments in Ethiopia prohibit the use of scientific calculators and formula sheets, requiring Grade 12 students to rely on rote memorisation and manual arithmetic. This policy creates unnecessary cognitive load, making science appear overly complex and computational. Drawing on Cognitive Load Theory and Self-Determination Theory, this study examines whether cognitive scaffolds can help students focus on meaningful learning and higher-order reasoning. This 16-week quasi-experimental study at Higher 23 Secondary School in Addis Ababa, Ethiopia, introduced the experimental group to Casio fx-82MS scientific calculators, structured formula sheets, and Student Teams Achievement Divisions collaborative learning. The control group continued under standard conditions. Data from a standardised 40-point exam and the Physics Motivation Questionnaire II were analysed in R using Analysis of Covariance to control for baseline differences. The experimental group outperformed the control group, with a mean score of 61.20 versus 44.12, a difference of 17.08 points, and a very large effect size. Motivation improved from “Moderate” (1.89) to “Good” (2.57), with increases in self-efficacy (2.40) and intrinsic motivation (+0.91). Analysis of Covariance confirmed a 14.1-point advantage for the experimental group after adjusting for baseline scores. Reducing routine arithmetic allowed students to excel at tasks requiring analysis and evaluation, especially in complex topics such as impedance in alternating current circuits. Student Teams Achievement Divisions sessions improved self-efficacy by distributing cognitive tasks and supporting peer verification. However, a significant gender disparity emerged, with male students achieving greater gains than female students. Policymakers are advised to: pilot the structured use of scientific calculators and formula sheets in secondary physics exams; revise national assessment guidelines to emphasise higher-order reasoning; and invest in professional development for teachers to support the effective integration of tools and promote gender equity.