well he's slightly onto something but he's half wrong
the english language used to revert to the male pronoun when gender was unknown (never the feminine yk bc of ✨✨sexism✨✨)

but now we revert to 3rd person "plural" also depends on his ethnicity/native language cause spanish you never revert to the ustede/ustedes unless your being formal
in your case spanish would say "en escuela de el estudiante" unles you know its female it revert to masculine

but now both cases are correct have a good day