No place offering anyone a job is a guarantee.
None - zero, zilch - short of nepotism.
But Jane Street, like most everywhere, has non elite s hoop employees.
But can you take it ? Unless they’ve changed - yes.
We have no idea what might happen from there.
Anyway, back to my point, OP can cull a lot of schools. Getting into a ‘name’ for IB likely isn’t an issue although getting a job will be.
Quant finance might require an entirely separate major/skill set.