The principal of DeWitt Clinton HS, a struggling Bronx school in Mayor de Blasio's multimillion-dollar Renewal program, changed students failing grades to passing without teachers knowledge or consent, insiders told The Post. In one case, Santiago Taveras gave a senior who received a "no show" in a global-history class a 75 and changed her failing 55 grade in gym to a minimum passing 65, records show. She then got a credit for each class, which she did not deserve, several staffers charged. He thinks he is God and can do whatever he wants. ... Taveras changed a students failing 55...