4.15协议
什么是“4.15”协议
1999年，美国多家大学联合制定并实施针对外国学生的“4·15协议”，主要内容为：申请赴美留学、已拿到多个学校录取通知书的学生，必须在4月15日前决定一所你要去的学校，否则，所有录取通知书将都被视作无效。这个“协议”的用意，是约束某个申请人同时接受多个学校的录取，但直到开学前才通知其中一些学校“无法按时就读”的不当行为。申请人的这一做法将大大影响学校正常的招生、教学秩序，也让美国每年白白放空大笔奖学金。当然，他们还损害了本国申请者的形象，为后来的申请者带来麻烦。
“4·15协议”主要内容
在每年的4月15日之前，申请者可以在已录取他的学校中任意选择一家就读，但明确答复所选大学的时间应不晚于4月15日，还应尽可能早地把自己的决定通知别的学校。留足时间，将已经收到录取通知书但决定拒绝的学校的各类录取资料，包括I-20表格，在4月15日之前寄回（材料不一定要在4月15日之前到达被拒学校，但事先必须用电子邮件通知学校）。如果在接受一所学校的录取之后反悔，受损害的学校有权请求所有签署“4·15协议”的其他大学拒收该生。
“4.15”协议原文（官方网站公布）
Acceptance of an offer of financial support (such as a graduate scholarship, fellowship, traineeship, or assistantship) for the next academic year by a prospective or enrolled graduate student completes an agreement that both student and graduate school expect to honor. In that context, the conditions affecting such offers and their acceptance must be defined carefully and understood by all parties.
Students are under no obligation to respond to offers of financial support prior to April 15; earlier deadlines for acceptance of such offers violate the intent of this Resolution. In those instances in which a student accepts an offer before April 15, and subsequently desires to withdraw that acceptance, the student may submit in writing a resignation of the appointment at any time hrough April 15. However, an acceptance given or left in force after April 15 commits the student not to accept another offer without first obtaining a written release from the institution to which a commitment has been made. Similarly, an offer by an institution after April 15 is conditional on presentation by the student of the written release from any previously accepted offer. It is further agreed by the institutions and organizations subscribing to the above Resolution that a copy of this Resolution should accompany every scholarship, fellowship, traineeship, and assistantship offer.
4.15协议主要是针对拿到了学校的财务支持(financial support)的学生，这些学生必须在4月15日之前给予学校答复。但对于只收到admission而没有任何financial support的学生则不受这个限制。