The consistent findings in all PISA results since 2000 indicate that class size is not the most important factor related to cognitive as well as non-cognitive student erformance. It appears that class size is a direct function of the birth rate of each particular participating country. Those countries with a lower birth rate maintain smaller classes and thoes with a higher birth rate maintain larger classes. Thus, class size is apparently a combination of demographics and budget with demographics the more potent factor.
Latent indications of PISA results indictae that teacher salary indicates, inter alia, social staus and respect that the general population has toward teachers and the teaching profession. Where teachers are well paid the general status of teachers is higher reulting in taechers being more motivated to expend effort in their classrooms. Where sa;aries are lower, teacher status is lower with teachers less motivated at their jobs.