It would depend on the 'high school' of your choice. Having said, below is a general 'key stage 2' level threshold tables below convert test marks into national curriculum levels for 2009.
English
Reading
Level Mark range
N 0-11
3 12-18
4 19-30
5 31-50
Writing
Level Mark range
N 0-10
3 11-24
4 25-35
5 36-50
English overall
Level Mark range
N 0-19
2 20-22
3 23-43
4 44-66
5 67-100
Mathematics
Level Mark range
N 0-14
2 15-17
3 18-45
4 46-76
5 77-100
Science
Level Mark range
N 0-17
2 18-20
3 21-39
4 40-62
5 63-80