Is 45 a good score on college placement test?

Whether a score of 45 on a college placement test is "good" depends entirely on the test itself. There's no universal scoring system. Each college or university, and sometimes even each individual test within a college's system (e.g., math placement vs. English placement), will have its own scoring scale and benchmarks for determining placement levels.

A 45 might be excellent on one test, indicating readiness for advanced coursework, while on another it might be considered low, requiring remedial classes. You need to look at the scoring rubric or percentile ranking provided with your results to understand what your score of 45 means in the context of that specific test. Contact the college's admissions or testing office if you're unsure how to interpret your score.