I was a science teacher too, but it came up in our curriculum. Managed to keep it as an option subject for last four years, got three groups in yr11 next year and two in yr10.
Anyone can offer it as an option but you need space, setup money, decent budget for feeding etc, weekend and hols cover (I have two lovely ladies that do half each), which is why it's not commonly done. Definitely possible and the kids are superb with animals around site (one snowball, chucked at a pig, in four years!)