All Masses are liturgies but not all liturgies are Masses.
According to the Catholic Encyclopedia liturgy is “the public official service of the Church.” These can take many forms: Mass, Divine Office, adoration, etc. So while it it is somewhat appropriate to call Mass a liturgy it can be confusing to some as to what’s taking place.
It should be noted that Eastern Catholics refer to the Mass as the Divine Liturgy. If the school in question is run by Eastern Catholics they would be 110% correct in referring to the Eucharistic sacrifice as “liturgy” since that is the word they use for it. But normally in the western Church we would call it Mass since the word liturgy for us can be several different things.
