Would be interesting to look at the 'stresses' that occur within schools. My 11 year old daughter was born on the 30th of August. Ergo she is the youngest in the year at school. She is studying with people that have a year of development on her. She is doing fantastically well but works hard to achieve that result. My hypothesis is that the age cut off in schools, unduly puts stress on the younger children in a class…
I'd think the opposite. Since she is used to having to work hard from a young age, she will be more successful in life. Others who coasted through—whom were used to everything being relatively easier—will not have the experience she has already accrued when faced with a harder challenge.
This would then reflect in a shorter lifespan.
Note however that this concept she would gain the tools for hard working in itself is flawed. Studies have shown that those born in the Summer months have statistically lower exam scores.