Wahrscheinlich irgendein stellvertretender irgendwas. Was genau, verrät wahrscheinlich der Kontext ...

...würde ich mal ohne Kontext sagen...

'principal', especially (Amer.) [educ.] = der Rektor | die Rektorin

'vice' = Stellvertreter, Stellvertretung, stellvertretend, stellv.

. . .

Since several of these words can have two meanings, perhaps it would help to say for the record that (with no other context, as a default) the person meant is the second in command of a school in AE. Another term for the same job is assistant principal. The BE equivalent IIRC would probably be something like deputy head(master/-mistress).

Stellvertretend here is used in the sense of 'von Amts wegen,' not 'vorübergehend' (= acting).

Rektor here is used in the sense of 'Schulleiter,' not of an administrative post at a university.

dann fassen wir doch zusammen und sagen;

stellvertretender Schulleiter

And in Germany, the title 'Rektor' is not only used at 'Universities' but also at 'Schools':

head teacher [educ.] = der Rektor | die Rektorin
headmaster = der Rektor
schoolmaster = der Rektor

Daddy,

das musst doch jetzt nicht sein; hängt doch von der Schulform ab: heißt also back to square 1!

>>the title 'Rektor' is not only used at universities but also at schools

Right, that was my point, or rather, the other way around: not only at schools but also at universities. So if you used that translation, you might need to specify 'Rektor (einer Schule),' because the AE word 'principal' is only for a school.

hm,

sage ich doch alles ganz kurz in 6!!

It does depend on the English speaking country...
In 1991, I was asked to bring my church's regards to the principal of Union Theological College, Bangalore, India. At that time, the institution was supposed to be an academic entity in its own right, though affiliated to some full-fledged university.
When I reached Bangalore on my round-trip through Southern India, I was invited to stay at the vice principal's house. Though the principal's title would have translated to "Rektor" in the German university system, there was no suitable translation of "vice principal". Judging by the tasks and powers they had, the closest comparison would have been a "Prodekan".

In other words, it'll all depend on the context and the system it is situated in.

***

anne, gib doch mal mehr Kontext (Hintergrund). Sonst schlagen wir uns hier ganz unnötig darum, wer alles Recht hat. Bisher m.E. alle...