i don't get why japanese students must declare their career path to the school
Some schools apparently have different classes based on career path in third year. In Oregairu there's small arc or sub-arc where all of the girls are trying to find out what Hayato's choice was so they could get in the same tract as him, Liberal Arts vs Science.
It's also probably a cultural thing. Schools are FAR more involved in students' lives in Japan than in the US. One site I read compared what happens when a kid is caught shoplifting.
US:
- Police called by store
- Police call parents
Japan:
- Police may or may not be called
- High School called
- Homeroom teacher apologizes to store
- High School calls parents to come in for a meeting
- Parents apologize and pay restitution to the store
- Student suspended for damaging the reputation of the school
Edit: This is why those "blackmail" plots that we think are totally stupid are more realistic in Japan.