After graduating from Dartmouth College in 1860, Bancroft became the principal of the
Appleton Academy in
Mont Vernon, New Hampshire. While principal he met his future wife, Frances A. Kittredge, one of his students. In 1867 he quit his job to marry Miss. Kittredge and move to
Lookout Mountain, Tennessee, where he would become principal of the Lookout Mountain Educational Institution. The school ran out of funds in 1872 and the founder quit the project, leaving Bancroft unemployed. Thus he decided to take the next year abroad in Italy. A year later in Halle, Germany (probably
Halle, Saxony-Anhalt) he received a cable message with an offer for principalship at Phillips Academy. He had the opportunity to stay in Italy but in reflection, he felt the choice to move was natural. During his time in Andover, he was offered a similar position at
Pacific University in
Forest Grove, Oregon, but declined.
Phillips Academy Bancroft accepted an offer from the Trustees of Phillips Academy while in Italy and was officially named 8th Principal on May 17, 1873. He began his tenure later that year, arriving in Andover on July 31, 1873, living in Double Brick House. He came at a time of decline for the school. Funds were low, student enrollment was decreasing, and the school's reputation was falling. As Principal, he took advantage of the school's centennial celebration in 1878 to launch a campaign, reaching out to alumni, decedents of alumni and founders of the school, and others. Over the next two decades he brought about the creation of new buildings, increased the size of the faculty from eight to 22 and the student body from 237 to over 400, and added significantly to the endowment, all of which added to the quality of education. Bancroft was a trustee of Dartmouth College, the Andover Theological Seminary, the State Hospital at Tewksbury, and the State Farm at Bridgewater. ==Personal life==