9 acres with 12 ewes and 15 lambs is quite under stocked really. I’d shut them up in it tight if you want it grazed hard, so paddock grazing and daily moves. For example we are currently grazing hard a 2 acre field, split into 2 paddocks, with 35 ewes and 40 lambs. The grass had got away from us as we couldn’t graze it until now due to ground conditions. They’ve done a week in the first acre paddock and aim to move them after 9 or 10 days. Then do another week-10 days in the second acre paddock. Then rest for a month or so.
You’ll need electric fencing, there’s no real way around it. We’ve got miles of the stuff
and a good fence unit, we’re currently using a 5 joule energiser with a big deep Earth stake.