<p>AS the city's public school students walk out the door this week to begin their summer recess, teachers will be doing the same and a good many of them won't be coming back. </p>
<p>Each year the city finds itself short of teachers. It's not because there's a shortage of people interested in teaching, or a lack of recruitment programs. Last year, 12 percent of Yale's graduating class, and 8 percent of Harvard and Princeton's, applied for 3,500 Teach for America jobs.</p>