While school is time consuming, it is also year round and not seasonal like most vaccinations. What would you do if someone missed the deadline to get vaccinated? The government has a very difficult time trying to enforce other deadlines that are not being met.
Vaccines should not be required. Why? Because it would be expensive and time consuming to make sure everyone vaccinated. Also, it should be a person's choice if they want to have a weakened strain of a virus inside their body or not. Even though vaccines can be helpful, it doesn't mean they always are. If vaccines were required it would also be difficult to decide how much everyone would pay for them, or if they had to pay at all based on their income.