The Portland School Board will vote Tuesday on a proposed $16 million building purchase for the Center for Black Student Excellence. Portland Public Schools’ proposal is to acquire the One North development at 3506-3514 N Vancouver Ave. and 25 N Fremont, St, in the heart of the Albina neighborhood. The development comprises two buildings, both constructed in 2015, with about 72,000 square feet of space, according to a district staff memo. (An appraisal the district obtained in May valued the property at $15.2 million.)