Write SQL query to solve given problem: How many Rock Hill City School projects have teacher donors?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT COUNT(DISTINCT T1.teacher_acctid) FROM projects AS T1 INNER JOIN donations AS T2 ON T1.projectid = T2.projectid WHERE T1.school_city = 'Rock Hill' AND is_teacher_acct = 't'