A dozen children are pre-enrolled for a public 4-year-old preschool program slated to start next fall at Bolinas-Stinson Union School District—enough potential students to get planning underway for the free program. Yet two other area preschools are worried about how it will impact their enrollment. 

The program will be the county’s only free preschool that is not restricted by income; other public programs—there are six in the county either underway or getting underway next year—are…