英语翻译students who have not completed one term of study at the

students are not advised to file for permission to transfer until they have completed one term.
不建议学生们在完成一学期前申请转学
students （ who have not completed one term of study at the school） are not advised to file for permission to transfer until they have completed one term
不建议（还没有在此校完成一学期的）学生们在完成一学期前申请转学
students （who have not completed one term of study at the school （ that issued them their first I-20 ）） are not advised to file for permission to transfer until they have completed one term
不建议（还没有在（最开始给留学生办了I-20的那个）学校完成一学期的）学生们在完成一学期前申请转学

尽管这段文字想要表达的意思十分清楚，不过语句结构很不专业，不分析也罢，您千万别学他。
意思很明白：
那些还没有在原始发出 I-20 的学校读完一学期的学生，在该学期结束前先别急着申请转学许可。
not advised to ... 虽然是不被建议（如此作）的意思，其实是间接暗示他们申请了也没用啦。
I-20 是美国大学或研究所对外籍学生给予签发的入学签证许可（属于移...