The target group included six of grade 1 students, who were studying at Ban Bueng-neum-bueng-krai-noon
School, and attending 5 classes of Length Comparison in the second semester of 2010 academic year. The school
has been participating in the Project for Professional Development of Mathematics Teachers through Lesson Study
and Open Approach supervised by Center for Research in Mathematics Education (CRME), Khon Kaen University
since 2007 academic year.