Another way to do this by reading the file a line at a time:

$ echo "Column1 Column2 Column3

2870      S11      1
574       S11      2
317       S11      3
31        S11      4
1         S11      6
1         S11      7
2925      S12      1
8         S12      5
1         S12      6
1         S12      9
" | perl -e'
use warnings;
use strict;

my ( @lowest, @highest );

while ( <> ) {
    next if /^\D/;
    my @fields = split;
    unless ( @lowest ) {
        @lowest = @highest = @fields;
        next;
        }
    if ( $lowest[ -1 ] >= $fields[ -1 ] && $lowest[ 0 ] < $fields[ 0 ]
+ ) {
        @lowest = @fields;
        }
    if ( $highest[ -1 ] < $fields[ -1 ] ) {
        @highest = @fields;
        }
    }
print join( "\t", "Lowest:", @lowest ), "\n";
print join( "\t", "Highest:", @highest ), "\n";
'
Lowest: 2925    S12     1
Highest:        1       S12     9
[download]