Mater Dei School | 198 followers on LinkedIn. Mater Dei is an elementary school for boys grades 1 through 8, conducted by Catholic laymen, in Bethesda, Maryland. Mater Dei School intends to provide an accelerated yet basic Catholic education in which character development is emphasized and appreciated as much as academic accomplishments. In a traditionally structured yet relaxed atmosphere, the students are encouraged to both work and play hard; accordingly, a strong athletic program complements the scholastic curriculum.