Most of the medium size birds can be taught to tolerate alone time. The main things will be how much time you spend with them while you are there, how many toys and things to keep them entertained can you provide, keeping a consistent yet flexible schedule, etc.
If you could say spend a half hour to hour before going to work with your bird and then a couple hours in the evening then you leaving during the day shouldn't be too stressful especially if they have plenty of toys and you leave a radio or TV on for noise. In that case I would probably lean more towards the senegal or maybe one in the conure family. The macaws even mini macaws seem more stressed by alone time. Some senegals or Jardines also show stress from this but will usually become accepting if given enough quality time together when you are home.
Just make sure that when you are home you spend plenty of time interacting. Even if you are grading papers or something if you can let the bird out of the cage or at least talk with the bird while you are busy, this should help. Also keep your schedules somewhat consitent during your breaks. If during winter or summer break you spend four hours a day interacting and then you go back to school and you can only spend one hour a day this causes more stress than spending two hours every day no matter whether you are on break or not!