RandiKnuth My apologies for not getting back to you earlier.
On the outbound, DXB/SFO EK225 the lowest published economy fare (called "X" fare bucket) is available from 6 December onwards. For the return trip in September (EK226) it is available any date 23 to 29 September (I did not check outside these dates). The problem however is that this is a fare with a maximum validity of 6 months so you will not qualify for it. The lowest fare bucket with a 12 month ticket validity is "R", which is more than double the price (base fare only, taxes should be the same)

I have never used promo codes myself, so I simply do not know how these work. Will they 'unlock' other fares, will they 'override' the 6 month validity? And will they check if you are a student and if so how? I can't help you with that, there may be others on this forum who have either experience with or knowledge of the 'promo code' system.