In the Singapore primary school Mathematics curriculum, students are taught the model method that uses bar diagrams to visualize the problem structure in a given word problem. When these students progress to secondary school, they learn the algebraic way of solving word problems. Studies (e.g. Ng et al.) have shown that poor bridging of students from the use of bar diagrams to the use of letter-symbolic algebraic methods can hinder their learning of algebra. We design a software tool "AlgeBAR" to scaffold the learning of the algebraic process, especially the formulation of equations to support a pedagogy that seeks to help students transit from bar diagrams to algebraic methods. In this paper, we report a cycle of evaluation of the intervention pedagogy by examining a class that uses the software tool as part of a holistic intervention package. This evaluation is in the context of an overall design research approach that sought to address complex problems in real classroom contexts in collaboration with practitioners and to integrate design principles with technological affordances to render plausible solutions. Our findings show that the software tool can be an important enabler of the bridging process.