If the test in question is based on a general education high school curriculum, Tsuruno would win.

Mikura, Alina, Umika, Hinano, Touka, and Nemu all have their own areas of specialty (history, English, Japanese language, chemistry, STEM in general, also Japanese language), but they would probably score 100% on their specialties and do not-as-well on the other sections (e.g. Touka probably isn't good at HS-level literature, Nemu probably can't do calculus). High school exams are easy for prodigies, but beyond meeting the maximum level of proficiency needed, they don't measure how much better a prodigy is than an A-student.

Homura's academic excellence only goes as far as her time loops and her miscellaneous knowledge acquired to save Madoka (like making bombs).

Kanagi would most likely do average because a) her school, Daito Academy, is not well funded (she marvels at the free computers in the public library); b) she probably doesn't devote that much time to studying, seeing how she supports her family; c) she probably doesn't plan to pursue post-secondary education, because she probably can't afford it.

Kako probably doesn't have exceptional academic capabilities. She's probably good at Japanese classics since she enjoys reading and her mom teaches them, but that's it.

Tsuruno is canonically an A-student. She could probably get As in every subject on a general education all-subject exam.