CREATE TABLE list (lastname TEXT, firstname TEXT, grade DECIMAL, classroom DECIMAL)
CREATE TABLE teachers (lastname TEXT, firstname TEXT, classroom DECIMAL)

How many students are taught by teacher 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" AS "T1" JOIN "teachers" AS "T2" ON "LEIA" = "T2"."lastname" AND "T1"."classroom" = "T2"."classroom" AND "T2"."firstname" = "TARRING"