What to teach first: theory or practice?
It isn't really a question of either or in terms of theory and practice. Instead, what is needed is theory and practice happening simultaneously in the classroom. The students learn a concept and then they used it immediately in some sort of authentic assessment. To have to what 1-2 years to use any sort of new knowledge is difficult for the average young adult learner and nearly impossible for a mature adult learner. Knowledge retention is most effect through teaching it to others and followed next by the application of it.

Within education, there is a big emphasis on learning by doing or being an active learning. This can take many forms such as the use of projects, problem-solving, presentations, etc. The point is that the students need to learn through actually doing or producing something through some sort of authentic real-world application. The real-world application creates the relevancy that most students need in order to process whatever it is that they are learning. This is particularly true for inexperienced students who have zero practical knowledge.

A major exception to this is the experienced student who returns to gain theoretical insights into their career. For example, if a teacher returns to school for a master's in education, they often experiences many "aha" moments when they see a connection between a theoretically concept and something that happened when they were teaching. Since these people already possess practical knowledge they are even better able to appreciate theoretical knowledge and create a bridge between the two.