There's a noexit sign from the main road A52 visible on https://www.mapillary.com/app/?pKey=EcwMkTF1UA4hwtzX8yCv4Q&focus=photo&lat=52.9336583&lng=-0.8108173&z=17&x=0.8134125213129502&y=0.590622541331697&zoom=3. Where the barrier might be located is harder to say, but probably they did not want any traffic passing the school site.