Using mixed method design, this study determined the extent of the implementation of the curriculum guide in Mathematics 10 classes, the alignment of learning competencies, instruction and summative assessment, identified the challenges encountered by the teachers, and developed a Curriculum Implementation Monitotring Plan. Questionnaires and documents of teachers from eight public schools in the Division of Nueva Vizcaya during School Year 2017-2018 were utilized. The results revealed that the teachers fell short of the required time in implementing learning competencies of the K to 12 Mathematics 10 curriculum guide due to disruptions of classes, although interventions were done to address the issues. Among the learning competenceis in Mathematics 10, the least implemented were the learning competencies of statistics and probability concepts where teachers spent about one-third of the required time. Most of the instruction and summative assessment employed and administered by the teachers were aligned with learning competencies. The most pressing challenge in the implementation of learning competencies was time while in the delivery of instruction was students' skills and knowledge and the most pressing concern in developing summative assessments was related to students' attitude. A Curriculum Implementation Monitoring Plan was proposed to oversee the implementation of K to 12 Basic Education Curriculum towards development projects.