St. Mildred's-Lightbourn School was founded by a community of Sisters, who had traveled to Canada from various parts of England.

In 1923, Appleby College Headmaster, John Guest, requested for Ruth Lightbourn, who was staying at her parents' house, to teach his two daughters.

She continued teaching young children from well-to-do families, in an expanded area, for thirty-seven years later.

Throughout the year, girls have the opportunity to participate in a variety of opportunities to test their academic abilities which, depending on the year, include challenges such as math contests, bridge building, the Spelling Bee of Canada, the CIS Junior Speech Competition, Kids Lit Quiz, music festivals, dance festivals, and more.

Open courses are designed to prepare students for further study in certain subjects and to enrich their education generally.

Technology is integrated throughout curriculum in all subjects to continue education beginning in the junior and middle schools.

All senior school students have their own personal laptop equipped with an SMLS suite of installed software.

Student's curricular use of technology includes the following, among others: video and digital cameras, tablets, interactive projectors, sound recording, TI-83+ calculators, scientific probes, and GPS units.

St. Mildred's offers a variety of opportunities for students to participate in exchanges and travel to other areas on the globe.

Then in JS4 and beyond, girls may go to various trips such as overnight camping, high ropes courses, winter survival skills, and learning to paddle a variety of watercraft.