one reason why the association is weak even before accounting for the socioeconomic profile of students and schools is that the relation is curvilinear students who had spent too little time less than one year in preprimary education score lower in science than students who had not attended or who had spent more than one year table this only covers expenditure on educational institutions these resources are allocated throughout a students educational and countries spend different amounts per student caution is required in interpreting this indicator as school systems are organised in many different ways across countries