Information about free special testing of children ages 2 to 4 is available from the following sources:

ALEXANDRIA: A preschool learning clinic to test children is held the third Tuesday of each month at the school administration building, 3801 W. Braddock Rd., from 10 a.m. to noon. No appointment is necessary. For information, call 998-2175.

ARLINGTON: Screening of children is done in the home. To set up an appointment, call Lynn Owings, preschool helping teacher, at 558-2683.

FAIRFAX COUNTY: Preschool screening is held in conjunction with kindergarten registration each spring. In addition, screening is conducted by appointment year-round at the Devonshire Center, 2831 Graham Rd., Falls Church. Call Sarah Brogan at 560-5344.

LOUDOUN COUNTY: A screening clinic is held each spring. Parents, doctors and community agencies may also refer preschoolers at any time for individual testing in the home or at school offices. For information, call Mary Kearney, supervisor of special education, at 777-2290.

PRINCE WILLIAM COUNTY: Initial testing of preschoolers is done by appointment from 9 a.m. to 3 p.m. every Tuesday at two locations: Kilby Elementary School in Woodbridge and New Dominion School in Manassas. Testing also is done Wednesdays and Fridays on a rotating basis at other local schools. For an appointment, call Betsy O'Dell, preschool coordinator, at 791-3151.