Problem 2:
SELECT H.grade, COUNT(*)
FROM Highschooler H
WHERE H.name = 'Alison'
GROUP BY H.grade
ORDER BY H.grade ;


Problem 3:
ID --> Name, Grade
ClubPresID --> ClubName
ClubName --> ClubPresID

It is not that case that ClubPresID --> ID because a club has several
members. You can't identify an individual just by know the president
of the club to which they belong.


Problem 4:
Many possibilities here...
Here is one possible set of classes (or tables). You do need two
different kinds of associations member-of and president
     +----------------+                 +----------------+
     |                |                 |                |
     |  Highschooler  | 1.*         0.* |  Club          |
     |    ID          +-----------------+    ClubName    |
     |    Name        |    member-of    |    ClubPresID  |
     |    Grade       |                 |                |
     |                | 1.1         0.1 |                |
     |                +-----------------+                | 
     |                |   president-of  |                | 
     +----------------+                 +----------------+
It is also possible to have a ClubPresident class (table) which
has associations with HighSchooler and Club.