How can I avoid duplicating multi-column correlated subqueries?

I want a correlated sub query that returns multiple columns and filters itself based on values in the main table.

A list of student test scores for a set of days:

create table student
(id, name     ); insert into student values
(1 , 'joe'    ),
(2 , 'steve'  );

create table testScore
(id, studentId, day  , score); insert into testScore values
(1 , 1        , 5    , 70   ),
(2 , 1        , 10   , 68   ),
(3 , 1        , 15   , 95   ),
(4 , 1        , 20   , 81   ),
(5 , 2        , 5    , 100  ),
(6 , 2        , 10   , 75   ),
(7 , 2        , 15   , 98   ),
(8 , 2        , 20   , 92   );
create index testScore_studentTopScores on testScore (studentId, score, day);

If I need to get the top test score for each student (and include the corresponding day numbers, and have the testScore_studentTopScores index be used) I would love to do:

select
  student.name,
  topScore.score as topScore,
  topScore.day as topScoreDay
from
  student
  left join (
    select * from
      testScore
    where
      testScore.studentId = student.id
    order by
      score desc
    limit 1
  ) as topScore
order by
  topScore desc;

And have it return:

But from clause subqueries can't reference outer/parent tables. Column subqueries and where clause subqueries are able to access tables in the from clause, but cannot return multiple columns. So I have to duplicate the subquery for every column:

select
  student.name,

  (
    select
      score
    from
      testScore
    where
      testScore.studentId = student.id
    order by
      score desc
    limit 1
  )  as topScore,

  (select day from (
    select
      score,
      day
    from
      testScore
    where
      testScore.studentId = student.id
    order by
      score desc
    limit 1
  ))  as topScoreDay

from
  student
order by
  topScore desc;

Neither SQLite nor MySQL can do this without duplication for each column. Microsoft SQL Server has an outer apply join operator; like a left join but where the clause can reference prior tables in the from clause. That's what I want in SQLite.

Also, the solution should not be an SQL trick to just handle this simple example. It needs to be general enough to be scalable for any large and complex query.

Efficient because it only needs one lookup for each student; jam columns I want into one JSON column and extract them later:

select
  topScore.name,
  topScore.topScoreJson ->> 'score' as topScore,
  topScore.topScoreJson ->> 'day' as topScoreDay
from (
  select
    student.name,
    (
      select
        json_object(
          'score', testScore.score,
          'day', testScore.day
        )
      from
        testScore
      where
        testScore.studentId = student.id
      order by
        testScore.score desc
      limit 1
    ) as topScoreJson
  from
    student
) as topScore
order by
  topScore desc;