slow subselects

Hello,

I'm having a surprising performance problem with the following simple
'highscore report'

select studentid, (select max(score) from
studentprofile prof where prof.studentid = students.studentid) from students;

I have indexes on students(studentid) and studentprofile(studentid).

Row counts: about 160 000 in each students and studentprofile.
Postgres version:
postgresql-8.1.8-1.fc5
postgresql-server-8.1.8-1.fc5

This is a dual-processor 3Ghz 64bit box with 2 GB mem.

Running the query takes 99% CPU and 1% mem.

I have the same data in MSSQL and there the query takes less than a
minute. With postgres it seems to take several hours.

Is there a way of making this faster?

Marko