In a press release form the Church

Dear Brothers and Sisters:

We desire to strengthen our beloved children and youth through increased faith in Jesus Christ, deeper understanding of His gospel, and greater unity with His Church and its members. To that end, we are pleased to announce that in January 2019 children will complete Primary and begin attending Sunday School and Young Women or Aaronic Priesthood quorums as age-groups at the beginning of January in the year they turn 12. Likewise, young women will progress between Young Women classes and young men between Aaronic Priesthood quorums as age-groups at the beginning of January in the year they turn 14 and 16.

In addition, young men will be eligible for ordination to the appropriate priesthood office in January of the year they turn 12, 14, and 16. Young women and ordained young men will be eligible for limited-use temple recommends beginning in January of the year they turn 12. Ordination to a priesthood office for young men and obtaining a limited-use temple recommend for young women and young men will continue to be individual matters, based on worthiness, readiness, and personal circumstances. Ordinations and obtaining limited-use recommends will typically take place throughout January.

We encourage local leaders to implement these changes throughout January 2019. Additional information is available at childrenandyouth.lds.org.

Sincerely yours,