St. Leo Catholic School is an Toronto Catholic District School Board elementary school opened in 1926 on Pidgeon (now Stanley) Avenue, in the parish of St. Leo's (the oldest Catholic Church in Etobicoke), with the school being the oldest existing Catholic School in Etobicoke; the older Highfield Catholic School on Etobicoke's border with Brampton having closed many years before St. Leo opened. For lack of funds, the original school building (still standing) was a copy of the older St. Patrick's Catholic Elementary School (demolished for Malton, now Pearson, airport) in what is now Brampton; technically St. Patrick's was the 'mother' parish of St. Leo's although early Catholics in Mimico preferred to attend church and school in Toronto or the local Etobicoke public school (now renamed the John English Junior Middle School). With the establishment of St. Leo elementary school, a Mimico Catholic School Board was also established for the one catholic school in Mimico. Originally St. Leo was served by the Sisters of St. Joseph who commuted, first from Toronto, later from their Etobicoke residence in Our Lady of Sorrows Parish (beside the early St. Joseph's Catholic Secondary School for Girls, Islington). The school grew in the interwar years despite the creation of new 'daughter' parishes and schools in New Toronto (St. Teresa's), Humber (St Mark's) and later, the Queensway (Holy Angels). The school sits on land donated by parishioners of St. Leo's parish who used the school for many events until the building of a parish hall in the 1960s, and was operated by taxes raised from Mimico Catholics by the Mimico School Board until it joined the Metropolitan Catholic School Board (now the Toronto Catholic District School Board) in 1967 when the Town of Mimico ceased to exist and the Sisters of St. Joseph were replaced by lay staff. One of the most celebrated former alumni of the school, hockey player and executive Brendan Shanahan, has maintained a connection with his home town and school. The school has celebrated its 50th and 75th anniversaries while the local parish is celebrating its 100th.