Due to the time constraint and lack of concise contextualized classroom behavior indicators, current typical primary school classroom behavior management practices are ad-hoc and lack historical data support. To circumvent these problems, we designed a tablet-based classroom behavior management system (CBMS) for a primary school setting. The CBMS aids teachers in establishing concise and consistent behavioral expectations based on teaching experience and expertise, thus allowing them to conveniently provide timely feedback on pupils' performance and log ratings on a daily basis. We conducted a 1.5 years field study in a primary school Chinese course in East China, in which 124 pupils in the first grade and four Chinese teachers participated. The analysis of recorded data indicates that teachers' daily behavioral ratings are positively correlated with their pupils' academic achievements. The behavior rating strategy and indicators in CBMS can act as a substitute in promoting pupil's academic achievements. Our proposed system shows the feasibility and potential of handheld computer-based assessment strategy in implementing cost-effective classroom organization practices for low grade-level primary school pupils.