It is effective to move your household registration a few years before the college entrance examination.

According to the relevant laws and regulations, you can't move your hukou before the college entrance examination, otherwise you will be considered as an immigrant for the college entrance examination, and you can't get extra points for the college entrance examination. If verified, you will be disqualified. The specific time depends on which provinces to visit, different working areas and different requirements. Some areas need more than one year in advance. According to the regulations, if a citizen moves out of the household registration jurisdiction, he or the head of the household shall apply for registration with the household registration authority before moving out, obtain a migration certificate and cancel the household registration. Citizens who move from rural areas to cities must apply to the permanent residence registration authority for moving out with the employment certificate of the urban labor department, the school admission certificate, or the approval certificate of the urban household registration authority.

Legal basis:

"Regulations on Household Registration in People's Republic of China (PRC)" Article 10 If a citizen moves out of the jurisdiction of the household registration, he or she shall report to the household registration authority for emigration registration, obtain a certificate of emigration and cancel the household registration before moving out. Citizens who move from rural areas to cities must apply to the permanent residence registration authority for moving out with the employment certificate of the urban labor department, the school admission certificate, or the approval certificate of the urban household registration authority. Citizens moving to border areas must be approved by the public security organs of the counties, cities and municipal districts where they live.