随着在美国大学的中国留学生越来越多，难免会有一些同学因为生病、或者其它原因而不得不休学，需要在完成学业前离开学校。另外也有一些学生因为在校表现差，GPA没有达到学校的要求，被学校withdrawal或直接dismissed。那这种情况下，这些学生的F-1签证是否还有效？如何再次进入美国？如何继续学业？

下面是哥大官网关于这种情况的具体说明：

Leave of Absence, Suspension, or Withdrawal from Columbia University by Students in F-1 Status

While in the United States, students in F-1 non-immigrant status must be continuously enrolled full time during the academic year until the completion of their programs of study. If you take a non-medical leave of absence, withdraw voluntarily, or are suspended or required to withdraw from the University, you are required to leave the United States within 15 days of this action. The only exception to these rules is a medical leave of absence.

If you take a leave of absence, withdraw from your program, or are given a suspension, you must contact the ISSO immediately to discuss your immediate plans and any plans you may have to return.

Medical Leave of Absence

The only LOA that allows you to remain in the United States as an F-1 student is an approved medical leave of absence while you receiving medical treatment in the U.S. The medical leave must be approved by your school. The ISSO requires confirmation from your school and a letter from your medical provider (licensed medical doctor, doctor of osteopathy, or licensed clinical psychologist) stating 1) your medical condition, and 2) advising the ISSO that you are unable to be enrolled during the semester the leave is granted. You are expected to enroll fulltime in the following term unless another medical leave of absence is approved for the following term. Under immigration regulations, no more than twelve months of medical leave are allowed per degree level. Medical leaves of absence must be approved by the ISSO in semester increments only.

Withdrawal, Voluntary Leave of Absence, Dismissal, Suspension

For all the above categories, F-1 students are required to depart the United States. Your current F-1 status is "terminated" in the SEVIS database and you will need to request a new initial I-20 to return to the U.S. Apply for your new I-20 certificate of eligibility online at http://isso.columbia.edu. Be sure to follow all the instructions on the web site. You will also need to pay a new SEVIS fee and have a valid F-1 entry visa to return.

When you return to the U.S. using your new initial I-20, you must report your arrival to the ISSO so that your new SEVIS is update to Active status. Submit the online SEVIS Report Form for New F-1 and J-1 Arrivals within the first week of your return to the U.S. This is very important as you will lose your F-1 status if SEVIS is not updated in a timely manner.

Important Considerations:

If you have not registered during the academic year for any reason other than a sanctioned medical leave of absence, you will not be eligible for practical training until you have completed one academic year in F-1 status.

If you wish to make short-term, temporary visits to the U.S. during the period that you are on leave, suspended or withdrawn from the University, you should not enter in F-1 status but rather on a different visa, such as a B-2 visitor's visa. You may enter in Student Status only if you are returning for the purpose of resuming your studies. 

If you have taken a medical leave in the United States, you are not permitted to engage in any student-based employment in the U.S., whether on-campus or off-campus, until you have been cleared to return to your studies. If you wish to take a leave of absence to pursue employment or any other activities in the U.S., you will have to change your immigration status accordingly and should speak with an ISSO adviser about your plans.

上面主要内容如下：

 除了病假外，不管是因为你自己主动申请离校、因休学离校，或是被学校开除等原因不得不在毕业前提前离校，你必须在该行为确定之日的15天内离开美国。你目前的F-1签证将会在SEVIES系统中被终止。如果你再次进入美国的话，你需要申请新的签证，除非你是回来读书，否则不得以学生身份入境，而且以学生身份入境的话也是需要申请新的I-20和F-1签证，SEVIE费用也需要重新缴纳。

因为医疗方面的原因休学离校者，不受上述规则限制，可以留在美国，但是在休学期间，不能以任何形式在美国打工或工作。

另外，不管什么原因休学或离校，一定提前和学校的国际学生办公室沟通好，了解学校的相关政策。争取不给自己找麻烦，不影响以后继续你的学业或是入境美国。

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