Here are some resources that are available online, either via this website or others.
1) There are not many resources that speak about this devotion, or its association with the “Brothers of the Christian Schools of Mercy.” However, this website about the shrine provides some context for this feast.
2) Two Lasallians articles speak about the 100th anniversary of the reconstruction of the abbey church of Our Lady of the Star.
3) There is a PDF prayer service about Our Lady of the Star.
4) The Motherhouse in Rome has provided a PDF with the liturgical (Mass) readings and prayers for this Lasallian feast.
The origin of the Sanctuary of Our Lady of the Star in Montebourg, Normandy, France, is lost in legend. A Benedictine monastery was founded there in the eleventh century and remained throughout the lower Middle Ages one of the four great abbeys of Cotentin. The sanctuary was demolished, along with the monastery, during the time of the French Revolution at the end of the eighteenth century. Both structures were rebuilt by the Brothers of the Christian Schools of Mercy, beginning in 1842. This diocesan community of religious teaching brothers, like the sisters of the same name founded by Saint Mary Magdalene Postel, followed the Rule of the Brothers of the Christian Schools of De La Salle.
They chose to be incorporated in 1938 into the Lasallian Institute. Today the Institute supervises the Lasallian schools in Montebourg, and the Association of Friends of the Monastery and Sanctuary acts as the custodian of this ancient Marian shrine. A number of Brothers of the Christian Schools are individual members of this association.