DeRay Mckesson, the prominent civil rights activist who last month was named interim chief human capital officer for Baltimore's public school system after an unsuccessful mayoral bid, was among more than 100 people arrested in Baton Rouge amid nationwide protests against police killings late Saturday and early Sunday. In a widely-circulated image of his arrest, the Baltimore native is seen on one knee, staring directly ahead of him wearing a T-shirt reading "#StayWoke" — a Twitter hashtag used to urge awareness of the political, social and cultural realities facing minority communities in America. Mckesson turned 31 on Saturday; he was...