MySQL SELECT IF statement

I have 4 tables; loans (has 'user_id'), users (has 'student_ID' and 'teacher_ID'), student, and teacher.

The code I tried:

SELECT *FROM loans LEFT JOIN users ON loans.user_id=users.user_id
(
IF student_ID='1' THEN (SELECT *FROM teacher)
ELSE (SELECT *FROM student)
)

The code is not working properly. I want the loans display the student or teacher name from users. I have tried similia work, and it doesn't work either.