Saturday mornings from 8:45-10:30 in December, January, and February at Great Brook Ski Touring Center, 1018 Lowell St., Carlisle, with or without snow cover. For children in grades K-8, the program involves building fitness for nordic skiing, developing proper technique and skills, and having fun on the trails of Great Brook Farm State Park. Cost is $50/child not including equipment which must be supplied by participants.