"The teacher debates with the student."
Translation:Die Lehrerin diskutiert mit dem Schüler.
If you mean that a teacher discusses with a university student (or someone studying at an equivalent institution in tertiary education), then your sentence is correct. If the teacher discusses with someone at school (primary or secondary education level), it is a Schüler.
In addition, the dative sing. form would be Studenten.
a young person is more likely to say "I'm at school" rather than "I'm a student".
That's quite a definitive statement for something I believe to be very dependent on the circumstances.
Although it's been a little while since I was at secondary school, I only remember saying "I'm at school" when I was within the school premises. And if someone would ask my occupation I'd say "I'm a student" long before I'd say "I'm at school".
P.S. Was there a particular reason you replied to this comment of mine? It's just that your comment doesn't seem to have anything to do with "der Student" being a weak masculine noun.
Why can't it be a female teacher talking with a female student?
As far as I'm aware it can be.
Die Lehrerin diskutiert mit die Schülerin
That, however, is wrong because you didn't use the dative after the preposition "mit". Your sentence would need to be:
Die Lehrerin diskutiert mit der Schülerin.
My answer was: "Der Lehrer diskussiert mit dem Schüler". My verb was wrong, but the offered translation was "Die Lehrerin diskutiert mit dem Lehrer", hence my remark about the gender of the teacher and the incorrect use of "mit dem Lehrer" in stead of "mit dem Schüler". I also note that the use "Student" as opposed to "Schüler" is very confusing.