Although it does not come as a surprise to those who have been paying attention on the Peninsula, the 2006-07 school year will go down in history. Why? This is the first time that Hispanic students outnumber white children in San Mateo County’s public schools, kindergarten through grade 12. According to data provided by the County Office of Education and the state of California Education Department, Hispanic youngsters make up 34 percent of the county’s total enrollment; white kids are 33 percent. The trend has been ongoing for well over 30 years here. The reasons: Steady Hispanic immigration and a relatively high birth rate in that population and a corresponding emigration of whites from the area and a lower birth rate in that ethnic category.