Is it "stack" of "stock" knowledge?

Don't be so sure that your teacher is always right, because then you run the risk of turning into a sponge and just soaking up the knowledge that your teacher gives you and then the quality of what you absorb is only ever going to be as good as what your teacher is giving you and then your education is dependent on the quality of your teacher - which to a degree is always the case anyway, but a student that questions the teacher and is inquisitive by nature is always going to learn more because it'll be the student's own investigation and inquisitive nature that guides your learning experience and that is ideal because you are learning how to learn and that is a skill that you cannot absorb, but must acquire.

Now... to answer your question, I believe the correct term is "stock knowledge", and that is not in the sense of stocking up knowledge - or stacking up knowledge for that matter - it is used in the sense of stock meaning 'grouping'. For example stock knowledge about issue A, would be basic standard knowledge about issue A.

Well done for questioning your teacher and it's great that you hold you teacher in such high regard but please realise that no one knows everything about everything and all humans are bound to get things wrong at some point in time. Your job as a student is to keep questioning and acquire the skills to find your own answers.

Good luck!!

-ian