I've collected scores of teacher constructed maths exams in over 10 different schools. My intention is to explore some home and school factors on these test scores. E.g whether or not parental involvement or higher perental education is related to the student's test scores... However given that the tests in these schools are not standardised (different difficulty levels), I'm thinking of using the z scores for my analysis instead... am I right? Or is there any other ways I can treat the test scores before running my analysis? What will be the statistical implications if I run a correlation/Anova analysis with the raw unstandardised test scores?
Let me clarify my question.....Each of these 10 schools conducted their own end of year examinations and scored students out of 100 . There's over 800 students in total. Data on background, attitudes , patental involvement, self efficacy as reported by the students have been collected....All I wanted to do is to find out if the each of the foregoing factors relates to the test scores ( am not interested in regression or any model building) ... is this statistically appropriate, when tests were different for each of the 20 school? That's my delima –