ellen levinson, andrew natsios, thank you both. >> woodruff: again, the major developments of the daye president biden joined 4000 people at an emotional memorial service for the m.i.t. police officer who was ambushed and killed in the manhunt for the boston bombers. and at least 87 garment workers died in bangladesh when an eight-story building collapsed. >> ifill: online, we have the first in our series on outstanding science and math teachers. hari sreenivasan tells us more. >> sreenivasan: a washington teacher transformed his third grade classroom into a new planet, turning his students into outer space explorers. the mission: to improve their science and math scores. that's on the rundown. and why are some evangelical leaders supporting immigration reform? ray talks to jenny hwang, co- author of a book about reform based on biicalrinciples. and on art beat, we talk to charles bradley, the 64-year-old singer known as "the screaming eagle of soul" who loves to give out hugs. all that and more is on our website newshour.pbs.org. gwen? >> ifill: and that's the "newshour" for tonight.