Hi shane,
As the field you want to filter is not a primary key, you cant fetch the entity directly but through a entitycollection. For exmample:
// the filter
PredicateExpression filter = new PredicateExpression(AcademicYearFields.IsCurrent = true);
// fetch
AcademicYearCollection toFindIn = new AcademicYearCollection();
toFindIn.GetMulti(filter);
// always will be only want current, so lets extract it
AcademicYearEntity theCurrentAY = toFindIn[0];