The Planning Board at its meeting on Tuesday will resume a public hearing on the expansion project that St. John’s Prep plans on its 175-acre Spring Street campus. The Catholic boys’ high school seeks to construct a new 74,875-square-foot science, technology, engineering, and math building for its high school, and to add a 300-student, sixth- to eighth-grade middle school in the existing Brother Benjamin Hall. The new building would be located next to the Ryken Center. The school is requesting approval of a major modification of the property’s site plan to accommodate the new building. The projects are part of a strategic plan for the school that also calls for construction of a wellness facility within five years that will include a field house, fitness rooms, and an indoor pool.