Speaking as someone who would be in the audience for such a devotion, I would suggest:
The daily bible reading, either from the hymnal or one chosen relating to what's going on at the school at the time
Perhaps a brief, 1-2 min, devotional reading/words of encouragement from you
An ample time for prayer - structured, but with the ability for everyone to name their concerns and wishes
Close with the Lord's Prayer and the Benediction.
My thinking is, as a worker, I come to the job with all the worries and care of the day to come on my shoulders. Rather than hearing someone else's words, or trying to concentrate on a liturgy when my mind is elsewhere, I would much rather have time to verbalize all of my concerns in the presence of my pastor and peers. Sure, one can pray those things individually, but that is nowhere nearly as confidence-inspiring as having the prayers of others added and being lifted up by a pastor. Versicles and Latin and antiphons have their place, but it doesn't sound like this may be it.
As far as texts go, others will have better suggestions than I, but I have my grandmother's old copies of The Days Worship and The New Day's Worship (1933 and 1963, respectively) by Charles Foelsch and find them to be a much stronger alternative to today's Portals of Prayer-type devotionals.