Howie Knoff said:

I am not in favor of extending the school day (or year) when students need the extra time to learn things they should have learned earlier in the day. . .  for example, when students did not learn because of:

• Disruptive or inefficient school schedules (including excessive numbers of transitions, and the constant flow of different groups of students in and out of the classroom during the day);
• Ineffective (initial) instruction (including when teachers are poorly trained, inexperienced, unprepared, or have too many different student skill levels to teach at the same time);
• Poorly designed curricula (including curricula that are not developmentally well-matched to the students, or when teachers are teaching students who do not have the prerequisite skills to succeed in the core curriculum); 

and/or because

• The students are unmotivated or disengaged (including when engaged students are in classrooms with disengaged students who disrupt instruction or create a negative learning environment). 

When these situations are present and the school day is extended to give students more hours of instruction, the additional time is basically compensating for gaps, weaknesses, or ineffective practices. This is inexcusable and should never occur as (a) it tacitly condones these debilitating conditions; and (b) will be unproductive if the same conditions persist during the extended hours.

via http://conta.cc/1DuoYHM

Image credit: timlewisnm