CREATE TABLE teachers (lastname CLOB, firstname CLOB, classroom NUMBER)
CREATE TABLE list (lastname CLOB, firstname CLOB, grade NUMBER, classroom NUMBER)

Find the number of students taught by TARRING LEIA.
SELECT COUNT(*) FROM list AS T1 JOIN teachers AS T2 ON T1.classroom = T2.classroom WHERE T2.firstname = "TARRING" AND T2.lastname = "LEIA"
SELECT COUNT(*) FROM "list" "T1" JOIN "teachers" "T2" ON "LEIA" = "T2"."lastname" AND "T1"."classroom" = "T2"."classroom" AND "T2"."firstname" = "TARRING"