Hmm. Incompetent teachers is a given ; however, there is a % of weak/ marginal workers in all business. Yes, tenure is one issue. Unions, in my experience, will not protect poor teachers IF THE STAFF / DEPARTMENT/ CHAIR MAKES IT CLEAR THEY WANT THST TEACHER OUT ( even when tenure is involved). So here is the issue: inner city schools often a tough assignments and teacher retention is huge issue. So those schools have many inexperienced teachers or teachers who do not have the resume to work at private or ‘successful’ public schools.

One more point. Test results can be so bogus because KIDS HAVE MO REASON TO DO WELL. STATE TESTING MEANS NOTHING TO THEM. SO AP LIFS BLOW OFF THE TESTS THAT ALWAYS CONFLICT WITH STATE EXAMS.