[perl 508]$ perl 498665.pl 
StID,SchooldID,TeacherID,KnowPre,KnowPost,Prefact
2,234,1001,,,
3,234,1001,,,
4,234,1001,,,
5,234,1001,,,
10,234,1001,,,
11,234,1001,,,
12,234,1001,,,
13,234,1001,,,
14,234,1001,,,
15,234,1001,,,
2..5,10..15,234,1001,,,