diff --git a/Entities/Contracts/Class.cs b/Entities/Contracts/Class.cs
index 45edfee..68d1269 100644
--- a/Entities/Contracts/Class.cs
+++ b/Entities/Contracts/Class.cs
@@ -2,9 +2,6 @@
 using System.Collections.Generic;
 using System.ComponentModel.DataAnnotations.Schema;
 using System.ComponentModel.DataAnnotations;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
 
 namespace Entities.Contracts
 {
@@ -12,20 +9,19 @@ namespace Entities.Contracts
 	public class Class
 	{
 		[Key]
-		[Column("id")]
-		public Guid Id { get; set; }
+		[Column("class_id")]
+		public int ClassId { get; set; }
 
-		[Column("grade")]
-		public byte Grade { get; set; }
+		[Column("grade_id")]
+		public int GradeId { get; set; }
+		public Grade Grade { get; set; }
 
-		[Column("class")]
-		public byte Number { get; set; }
-
-		[Column("description")]
-		public string Description { get; set; }
+		[Column("class_name")]
+		[MaxLength(30)]
+		public string ClassName { get; set; }
 
 		[Column("head_teacher_id")]
-		public Guid? HeadTeacherId { get; set; }
+		public int? HeadTeacherId { get; set; }
 		public User HeadTeacher { get; set; }
 
 		[Column("created_at")]
@@ -44,12 +40,11 @@ namespace Entities.Contracts
 
 		public Class()
 		{
-			Id = Guid.NewGuid();
-			Grade = 0;
-			Number = 0;
 			ClassStudents = new HashSet<ClassStudent>();
 			ClassTeachers = new HashSet<ClassTeacher>();
 			AssignmentClasses = new HashSet<AssignmentClass>();
+			CreatedAt = DateTime.Now;
+			UpdatedAt = DateTime.Now;
 		}
 	}
 }
diff --git a/Entities/Contracts/Grade.cs b/Entities/Contracts/Grade.cs
new file mode 100644
index 0000000..a98be1e
--- /dev/null
+++ b/Entities/Contracts/Grade.cs
@@ -0,0 +1,34 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace Entities.Contracts
+{
+    [Table("grades")]
+    public class Grade
+    {
+        [Key]
+        [Column("grade_id")]
+        public int GradeId { get; set; }
+
+        [Column("school_id")]
+        public int SchoolId { get; set; }
+        public School School { get; set; }
+
+        [Column("grade_name")]
+        [MaxLength(20)]
+        public string GradeName { get; set; }
+
+        [Column("grade_level")]
+        public int GradeLevel { get; set; }
+
+        // Navigation Properties
+        public ICollection<Class> Classes { get; set; }
+
+        public Grade()
+        {
+            Classes = new HashSet<Class>();
+        }
+    }
+}
diff --git a/Entities/Contracts/School.cs b/Entities/Contracts/School.cs
new file mode 100644
index 0000000..d6358f8
--- /dev/null
+++ b/Entities/Contracts/School.cs
@@ -0,0 +1,35 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace Entities.Contracts
+{
+    [Table("schools")]
+    public class School
+    {
+        [Key]
+        [Column("school_id")]
+        public int SchoolId { get; set; }
+
+        [Column("school_name")]
+        [MaxLength(50)]
+        public string SchoolName { get; set; }
+
+        [Column("address")]
+        [MaxLength(100)]
+        public string Address { get; set; }
+
+        [Column("create_time")]
+        public DateTime CreateTime { get; set; }
+
+        // Navigation Properties
+        public ICollection<Grade> Grades { get; set; }
+
+        public School()
+        {
+            Grades = new HashSet<Grade>();
+            CreateTime = DateTime.Now;
+        }
+    }
+}