Hey Ruston, I’m at a university College, so slightly different, however our budget and my time is below zero!
Some ideas though to help with managing things are:
Instagram – later.com and schedule out some posts, and then you can bulk with live things
Facebook.com – make use of the scheduling function too from natively in FB so that you can appear more active than you need to be
Batch process – meaning do a bunch of stuff at the same time (i.e. spend 3 hours at the beginning of the month scheduling/planning your Insta and FB and then it becomes very light in the end)
Copy stuff from your school newsletter.
Try and recruit students if you can as ‘in charge’ of photography and videography for events.
With social media – often consistency is more important than frequency, although for a school, I’d aim for about 3 times per week on whatever mediums you choose, although social media can be a huge time suck if you let it (and possibly for only limited ROI).