Is a 24 good score for the ACT Im sophomore in high school English-24 Math-21 Reading-25 Science-27?

A composite score of 24 on the ACT is a decent score, especially for a sophomore. It's above the national average, but there's definitely room for improvement if you're aiming for highly selective colleges.

Your individual section scores show some strengths (Science and Reading) and areas where you could focus your studying (Math). Focusing on improving your Math score would likely raise your composite score the most. Keep in mind that college admissions consider your entire academic profile, not just your ACT score.