I wonder if the term immature may start things off on the wrong foot. As with gifted kids it may be more overexcitibilities and asynchronous development ( http://www.sengifted.org/archives/articles/overexcitability-and-the-gifted )

In pre-school my son would play oddly or not at all with other kids and do his own thing sometimes during story time and sometimes get really emotional over seemingly trivial things. Sounds immature.

But what was really going on:
-> He was wanting to play more engaged complex things and the other kids were wanting to do parallel play.
-> At story time, the teachers were reading books a couple years behind where his comprehension level was.
-> They would emphasize letter learning, when he could sight read hundreds of words.
-> He had (still does) a strong sense of fairness and justice and will have strong reactions when those are violated, which seems to happen when other kids don't have the same understanding; and adults have standard responses for typical kids that age.
-> And yes when he gets emotional, he gets intensely emotional; just as when he thinks, he thinks intensely; when he focuses, he focuses intensely.

Take a regular eight year old and treat them and talk to them like a four year old day in and day out for a few months and ???