I know a lot about this vertical from the Google side. One thing you are going to run into is you are going to be indirectly and directly competing with people who are advertising very expensive courses and programs related to software engineering. This is a problem because with their courses being far more expensive they will be willing to pay far more in in terms of CPC. You may need to adjust your pricing structure in order to make sure to leave margin for yourself after advertising expenses.

Otherwise though I would say Google is going to be by far your most lucrative option.