Do most colleges require a student to take a language or can it be substituted with another class?

Most top colleges like Ivys and Elites want you to take 3 to 4 years of a language in high school (Havard wants 4). As you go down the rankings list you will see, some want 3 and others 2 minimum such as the UC Public colleges. So it depends on what kind of colleges you intend on applying to. I have not heard of any college allowing substitutions with other classes for a language requirement (pre-requisite).

I have watched some Youtube videos where someone who is a native Spanish or Chinese speaker has taken advanced AP Spanish or AP Chinese and scored a 5 on the AP exam or signed up for the SAT IIs and taken Spanish or Chinese and gotten 750+ scores and submitted those as evidence of language mastery. In this admissions cycle and future ones, the SAT IIs have been phased out completely and no longer available. Therefore, the only standardized test that colleges review on admissions applications is APs tests. I have read that even if you are Int'l student and speak Arabic or Hindi, you are required to both 1.) show mastery of English (TOEFL or IELTS) and 2.) have the 2 to 4 years of a 3rd language when applying to the better colleges.

I would write to the colleges you are interested in applying to to find out if they would accept a score of 5 on an AP Language exam as a substitution since I really do not know the answer. Also, keep in mind the AP Languages are only Spanish, French, Chinese, Japanese, German, and Italian (no one speaks Latin at home so that wouldn't count). So if you speak anything else at home, I doubt that they would accept your word of fluency as evidence of language mastery.

Other reports I've read indicated that if you speak Spanish or Chinese at home, that really doesn't count as a 2nd language on a college application and they want you to take a 3rd language that is different. I don't think anyone can prevent you from taking Spanish or Chinese for 4 years even if you are a native speaker but I'm certain that colleges that are Top 20 schools may mark down your application, saying that is a deliberate loophole you created to circumvent the requirement. They would not look at your language coursework as evidence of challenging course rigor and nor evidence that you took the hardest classes that were afforded you, both these things are the well-known criterion for evaluating the academic strength of the applicant.

It's important you do some direct research with the schools your targeting so you can make an educated decision on how to plan out your HS curriculum.

Good Luck