A Montessori school in Denver is warning parents about a possible mumps outbreak. The principal of Bright Horizons Montessori School sent a letter to parents on Tuesday saying there is at least one and possibly more cases of mumps at the school. The letter went over possible signs and symptoms of mumps that parents should look for. The letter also said some children could come down with a milder case of the mumps if they haven't finished getting their mumps vaccinations.