Portsmouth Priory (as it then was called) had a community of 24 Benedictine monks when I was there in 1955-58. All but two of the monks are in the photo above. The year before, Fr Aelred ("Barney") Wall, Headmaster, was in the photo; he switched to a more contemplative monastery in my senior year. The strength of the monastery may have peaked a few years later when Luke, Paul, Anselm and Gregory became novices.
The lay faculty numbered 16 in 1958, as indicated in the photo below. So of a total teaching pool of 30 (24 monks and 16 lay), three-fifths was monastic.
As vocations to monastic life have fallen off, and older monks have gone to their eternal reward, the ratio of monks to lay staff has reversed. The lay faculty today outnumbers the monks. On the Abbey web site five monks are shown as actively involved in the school, while the Portsmouth directory shows 116 on staff.
Since 1958, the number of seniors has grown from 35 to 94 in the Class of 2017. The teaching faculty has grown from 30 to 50, supported now by, it appears, 66 listed non-teaching staff.
Similar trends are observable in other monastic institutions. Ampleforth Abbey and College in England is one of the houses of the English Benedictine Congregation (along with Downside) that founded Portsmouth. Ampleforth is one of the largest religious college-preparatory schools in the country. The number of monks has fallen at Ampleforth, from more than 100 when I was there in 1952-55 to about 30 today.
At Ampleforth today, according to its Headmaster Fr Wulstan, who was in New York City this past week, monks are placed in roles where they can have a maximum influence on the spiritual life of the boys and girls at the school. Almost all of the teaching is now assigned to people who recruited for their teaching skills and academic background.