>>

>>select * from tests t1 ;
>>	where ;
>>	score = (select min(score) from tests t2 where t1.student = t2.student) ;
>>	or ;
>>	score = (select max(score) from tests t2 where t1.student = t2.student)
>>
>>* Not in older versions
>>select t1.* from tests t1 ;
>>	INNER join ;
>>	(select student, max(score) as maxScore, min(score) as minScore ;
>>	from tests group by 1) t2 ;
>>	on t1.student = t2.student and (t1.score = t2.maxScore or t1.score = t2.minScore)
>>

Cetin
>
>The last one is nice, but should you also group by testname in both cases?

No. Read the question.
Cetin