In the US, where penstemons originate, deer forage on them and, as far as I have been able to discover, they are not listed as poisonous in the various indexes of poisonous plants. As an ex-teacher myself, I fully understand Vonmarr's caution. Life could be very unpleasant for any school personnel who could be held to have caused the poisoning of a child, however, many warnings were given to that child.