You need this:
lstScores.Items.Add(students[index].ScoresList[i]);
Or the curly braces:
for (int i = 0; i < students[index].ScoresList.Count; i++)
{
s = students[index].ScoresList[i];
lstScores.Items.Add(s);
}
If you have more than one line in the body of your loop use curly braces. Your loop run four times but only add your last item because s
become equal to last item after the loop.When you don't use curly-braces only the first line that comes after the loop considered as loop body.So lstScores.Items.Add(s);
executing after the loop.