请问8老师和大家，如果以B2 visa入境，想上学，有有效的F1签证（两年前拿到，5年有效），如何调整身份？必须回国再入境吗？
-You can either file I-539 for change of status within US (it takes a long time) or just go out of US and reenter US using the F1 visa. I strongly suggest you to go out of US and reenter US using F1 visa up to 30 days before the new I-20 is effective (i.e. before the semester starts), thus you can study immediately as an F1 student.
可不可以从加拿大或墨西哥以F1签证入境？谢谢！-Yes.
