@Serge ********
, If you're sure they're not comin' back you can just show up at the airport with both passports and the letter from the school saying they are not studying anymore and get stamped out on the new passport.
The OFFICIAL way to do it though is to take them to the immigration office move the extension stamps from one passport to another THEN cancel the ED visa extension with documentation from the school saying the day they are flying out of the country is the date they stop studying.