Fluctuations and distortions in grade point averages (GPAs) can affect its usefulness as a measure of achievement. Against a backdrop of increasing internationalisation in higher education, such instabilities may be exacerbated by heterogeneous student populations and the varying role of language on English as a foreign language (EFL), content and language integrated learning (CLIL), and English as a medium of instruction (EMI) platforms. Accordingly, using descriptive and inferential statistics, we explored the distribution patterns of 58,324 grades awarded over a 10-year period at a major university in Bangkok, Thailand. We found evidence of longitudinal grade increase, grade compression, and grade disparity—all of which suggest the presence of grade inflation. Specifically, across the three teaching platforms, mean GPAs increased significantly as lettered grades compressed upwards, clustering around C and C+ levels. Grade disparity, meanwhile, decreased between courses and levels but increased between student populations (i.e., English majors were awarded significantly higher grades than non-English majors were). Based on our findings, we argue for more standardised assessment practices to tackle grade censorship and saturation, as well as potential elevations/reductions in graduating GPAs of admixed student populations. We also propose a new method to quantify and track mean GPAs through quartile measurements.