• A two-tailed paired-sample t-test confirmed that the difference in the two-year averages before and after for PFI schools is statistically significant.
• A two-tailed paired-sample t-test could not confirm that the difference in the two-year averages before and after for conventional schools is statistically significant.
• A one-tailed paired-sample t-test confirmed that the higher rate of improvement in PFI schools in comparison to conventional schools is statistically significant.