to find the data, go to Board Docs (the FCPS data repository) here:
http://www.boarddocs.com/vsba/fairfax/Board.nsf/goto? and open the FY18 Budget Questions, and look for Question #44 p. 120 where Elizabeth Schultz asks FCPS Staff to provide the number of unaccompanied minors placed in Fairfax County by U.S. Dept of Health and Human Services.
The numbers are; FY2014 - 1,373 FY2015 560 FY2016 1,321 and FY2017 671 for a total over this period of 3,925.
The average cost per pupil, excluding ESOL and Special Education is $11,450 and the ESOL cost per service for FY17 is $3,745 (see Question #47 p. 126)
So, $11,450 + $3,745 = $15,195/pupil * 3,925 = $59.6M Call it $60M (assuming none of these students needs SpecEd services)