You went to a school that had a thing about being progressive, and the head and governors were really into the idea of using the technology to 'expand people's horizons'. They figured having the boys spend some time experiencing having boobs, periods and the like would make them more understanding to the girls, and the girls getting dicks and male hormones would help them recognize what boys go through. The school even had access to nonbinary options, so you could try having both a cock and a pussy and boobs all at the same time, or having a flat chest and nothing there besides a hole to pee from, and see how all those suited you.
While they were kinda insistent about it, there was one bright spot- they had managed to wrangle it so that the changes were all paid for as part of your school fees. No one was quite sure how they managed it- the rumour was some shady deal with the county council- but in any case, at least the only things to get in the way would be students' discomfort with the changes they'd undergo.
Unfortunately, you had some discomfort about your upcoming change tomorrow. But who are you, anyway, and what are you worried about?