How to Retrieve Data Using "OR" Operator

How to Retrieve Data Using "OR" Operator

I have a question that I need your assistance.
Let's say if I want to find if the people in a certain district (districtID=5) has taken Course A (cID=11 or cID=12) BUT not both since they have the same course name with different cID, how do you write this in SQL, along with their FirstName, LastName and Email? Can you kindly help? Here are the fields:
peopleID   FirstName   LastName   Email                     schoolIDNum
1               Esther         B                b@hotmail.com      33
2               Tommy        L                 l@hotmail.com       55


registrationID1   peopleIDNum   sectionIDNum
22                      1                      40
23                      2                      40


sectionID   courseIDNum   districtIDNum
40              11                    5
41              12                    5


schoolID   districtIDNum
33            5
55            5


My codes below didn't work. It keeps giving me 0 rows. Any help or advice is appreciated.
SELECT p.FirstName, p.LastName, p.Email, s.CourseIDNum
FROM People p, Registration r, Section s, School sc
WHERE p.PeopleID=r.PeopleIDNum AND r.SectionIDNum=s.SectionID AND
(s.CourseIDNum=11 OR s.CourseIDNum=12) AND sc.SchoolID=p.SchoolIDNum AND
s.DistrictIDNum=2 AND r.Completed='Y'