如果美国签证没过期5年签证，sevis号变了，学校变了，需要从新面签么？

不需要。

详见：

Every student who applies for an F-1 visa for the first time will have the SEVIS number of the first I-20 issued written on that visa.  However, students may use the same visa (if it’s still valid) to leave and reenter the U.S.—even if they have a new SEVIS ID number—as long as they have not been out of the U.S. for more than 5 months.  That is the only rule regarding the legality of your visa that you need to be concerned about.  

You do need to pay a new SEVIS I-901 fee ($200) since you have a new SEVIS ID number.

需要，换学校都是需要重新申请学生签证的。