Most day care centers group children according to age for developmental purposes. Generally, infants from six weeks through one year and from one year through seventeen months are in a single room, which is partitioned to allow the toddlers a play area away from cribs. Mobiles and large manipulatives, such as balls or cubes, are provided for play and physical development. The next age group usually consists of toddlers from eighteen months to two years. This age doesn't generally initiate play with each other, but may follow the caregiver's lead in song and group activities. Socially, an important skill this age group is exposed to is toilet training. This activity should be initiated and consistently applied at home by parents, and reinforced by daycare providers during daycare hours. From this point on, groups are usually defined by age, the twos, threes, and fours each in separate groups. Daycare centers are allowed to determine advancement at their discretion. Many follow the traditional fall advancement program, just like schools. If you have any questions or concerns about the age group your child has been placed in, consult your caregiver.