Frantic Cantabridgians overloading Brookline schools?

Enrollment in Brookline kindergartens are up 25%. Is it because anxious Cambridge parents are moving to Brookline because they think the schools are better? Or is it simply because the Brookline School Committee lowered the age of enrollment for kindergarten a few years back? Jim Conley writes:

... Remember back in March of 2002 when the Brookline School Committee lowered the age requirement to attend kindergarten? Remember how nearly every kindergarten teacher in Brookline told the Committee that doing so would result in a flood of new registrants, many of whom will demand much more time from them? ...