Error Code: 1215. Cannot add foreign key constraint (foreign keys)

The most likely issue is this line:

FOREIGN KEY (classLeader) REFERENCES student(studentID),

The datatype of classLeader is VARCHAR(255). That has to match the datatype of the referenced column... student.studentID. And of course, the student table has to exist, and the studentID column has to exist, and the studentID column should be the PRIMARY KEY of the student table (although I believe MySQL allows this to be a UNIQUE KEY, rather than a PRIMARY KEY, or even just have an index on it.)

In any case, what's missing here is the output from SHOW CREATE TABLE student;

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There's a datatype mismatch.

The classLeader VARCHAR(255) column cannot be a foreign key reference to studentID INT.

The datatypes of the two columns has to match.

You are getting this error because of in FOREIGN KEY (classLeader) REFERENCES student(studentID) datatype of studentID and classLeader is different.Datatype of primary key column and foreign key column must be same.

From MySQL Site:

Corresponding columns in the foreign key and the referenced key must have similar data types. The size and sign of integer types must be the same. The length of string types need not be the same. For nonbinary (character) string columns, the character set and collation must > be the same.