How to improve SELECT performance on a big ORACLE view?
No, an order by in the view will not help. You may want to do two things. First of all you should ensure that student_number is indexed in the underlying table. Plus if the big view joins multiple tables you should ensure that the join columns are indexed. 

Second you may want to use a number like this:

WHERE student_number=123456


instead of 

WHERE student_number='123456'


if student_number is numeric to avoid type conversions.