Among the schools whose donators are teachers, what is the percentage of schools that are in Brooklyn?
donors are teachers refers to is_teacher_acct = 't'; Brooklyn is school_city; percentage = Divide(Count(school_city-'Brooklyn'),Count(school_city))*100
SELECT CAST(SUM(CASE WHEN T1.school_city LIKE 'Brooklyn' THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(T1.teacher_acctid) FROM projects AS T1 INNER JOIN donations AS T2 ON T1.projectid = T2.projectid WHERE T2.is_teacher_acct = 't'