Generally, there's not much developmental difference between children who are 30 months old and who are 36 months old. In specific cases, yes, there can be a significant difference, but since every child develops at different rates, it is entirely possible that a 30 month old child will be more advanced in some areas than a 36 month old. When the difference gets down to 3 months or less, the developmental gap will usually be so small as to be non existent.
There are, of course, exceptions to this. My son, 18 months, goes to a daycare where the next oldest child is 17 months. However, the 17 month old was born 2 months premature, and is significantly behind on many developmental milestones. My son is right on target for most physical milestones, and significantly advanced for verbal milestones. The contrast between the two of them is striking. However, they seem to get along just fine, and engage in parallel play (the other child tends to follow my son around whenever possible). This is a bit of an extreme example, though, and I think you'll find that most kids that close in age will be so similar that it will be difficult to determine who is older simply by watching them.
I could find no specific studies on the impact of being the oldest child in a daycare setting, but at wider age ranges it would seem to have some parallels with birth order within a family. On that count, there are actually studies that indicate the oldest child in a family tends to have a higher IQ. This is more likely attributable to the parental interactions than any social dynamic between the children, however.
This list of characteristics associated with birth order, however, might have more relevance since peer interaction seems to play a larger part:
- Is only child for period of time; used to being center
- Believes must gain and hold superiority over other children.
- Being right, controlling often important.
- May respond to birth of second child by feeling unloved and neglected.
- Strives to keep or regain parents’ attention through conformity. If this failed, chooses to misbehave.
- May develop competent, responsible behavior or become very discouraged.
- Sometime strives to protect and help others.
- Strives to please.
A study on family daycare in Israel did find some correlation between mixed age vs. homogeneous age daycare groups and the quality of the care provided:
The best quality of interaction between caregivers and children is found in groups where the difference between youngest and oldest child is between 13 and 24 months (M. Rosenthal, 1990). When the group was fairly age homogeneous and the children were mostly less than 2 years old, the caregivers usually offered a poorer quality physical environment, fewer educationally oriented interactions, less frequent group interaction, and were more restrictive, than caregivers caring for children age 2-3 in more age-heterogeneous groups. The children in these groups tended in turn to engage less frequently in fine motor play, have fewer positive peer interactions, and were somewhat more frequently emotionally distressed.
It seems that a wider range of children, particularly in the 2-3 year category your daughter is in, is preferable.
Along more anecdotal lines, I found this blog entry by a family childcare provider who feels that being the oldest in the group is a positive position:
Being the oldest in a group is a positive position that teaches a child a great deal.
- nurturing skills: taking care of others, being kind and helpful this oldest position builds life skills that all parents want their children to have.
- leadership skills: depending on where the child falls in their own sibling order or if they have a sibling, this could be the only time the baby, middle child or an only get’s to be the oldest. They finally get to facilitate play and branch out into areas of play that they may not have had an opportunity to explore before, it will promote creativity, and exploration.
- builds confidence: by giving a little responsibility with simple things, setting the table, helping the little ones with coats and shoes, you are setting up the oldest to succeed.
- hone problem solving skills: being the oldest, they finally get to practice all those skills with the young ones, how to share, use your words, and keeping things safe just to name a few. They get to practice and be the one that everyone looks to for the good example.