Generics rock and I believe they shine in more places than just in collections.  I was a little disappointed to see that you dropped generics all together!  [;)]

In addition, do you know about the new TableAdapters in 2.0....HOLY YES!  They rock as well.  Anyway, I wanted to throw my two cents out there.  This is one way you could implement your BOM:

   public class HighSchool {
       int iD;
       string principle;
       string name;

       public int ID {
           get { return this.iD; }
           set { this.iD = value; }
       }
       public string Principle {
           get { return this.principle; }
           set { this.principle = value; }
       }
       public string Name {
           get { return this.name; }
           set { this.name = value; }
       }
   }

   public interface IDataAccessLayer<T, K> {
       T Get(K primaryKey);
       void Save(T item);
       void Delete(T item);
   }

   public abstract class DataLayerBase {
       private string connectionString;

       public DataLayerBase(string connectionString) {
           this.connectionString = connectionString;
       }
  
       protected string ConnectionString {
          get { return this.connectionString; }
       }  
   }

   public class HighSchoolDataLayer : DataLayerBase, IDataAccessLayer<HighSchool, int> {

       public HighSchoolDataLayer(string connectionString) : base(connectionString) { }

       public HighSchool Get(int primaryKey) {
           throw new NotImplementedException();
       }
       public void Save(HighSchool item) {
          throw new NotImplementedException();
       }
       public void Delete(HighSchool item) {
          throw new NotImplementedException();
       }   
   }

In addition, you will notice that I was able to implement the interface implicitly which does not require the additional interface methods implementaion.

Hope this helps,

Jason