外國交流生

I am not an exchange student but am currently living abroad. I have friends who used to be exchange students and they mostly found the experience positive. Based on my personal experience, in schools, students tend to mingle with students from the same origin. In other words, students from HK usually stick with fellow students from HK. Obviously, when hanging out with people who speak the same language (Cantonese), it is difficult to learn good English. Living in a host family (where they all speak English) is an effective way to improve the spoken English skills. Staying in dorms may also work if the roommate speaks English. Practise makes perfect is definitely true.

Your daughter is 17 years old, so I assume she just finished Form 5. If she goes to the United States, she may very possibly be able to skip a year of school and go straight to Universities. Universities will assess her English skills and will also review her grades in Hong Kong. She also needs to take the Test of English as a Foreign Language (TOEFL). I have taken TOEFL before and it was not difficult (nothing compared to the SAT). If you need more information, please let me know. I am more than happy to help.

我去過美國做一年交流生. 是不錯的experience. 英文listening + oral 一定可以進步很多. 住家庭先自夠experience 美國人的生活. There's no guarantee that your host family would be good. But most American families are very nice. Don't expect them to be very rich, but they should be able to support you without charging you. They are like volunteers so they usually have a kind heart to take foreign students for a year -- to learn about your culture and treat you like you are a family member.
If you daughter wants to apply to an American university, it's actually quite easy to get into one. Of course getting into a pretigious ones depends on how good your daughter's grades are in Hong Kong.

唔好: 其實我想不到有什麼不好的地方 (exchange). 反而我覺得如果可以讀香港的大學就不用去外國讀啦. American high school is very very easy. If your daughter is good in academics in HK, then she'll probably find the lessons there to be extremely stupid/not challenging.