Retriving and saving Data In two Table having Parent Child Relation ?

you have several options:
1- you can do it manually. ie, you can write all DML codes yourself.
2- you can use a o/r mapper, or some other tool that it produces codes for you.

for example, you can use linq to sql. create a datacontext, manipulate it by using linq. but since you beginner, i advice you dirt your hands, code everything manually.

create table TEACHER (
	ID int identity(1,1) primary key,
	NAME nvarchar(10)
)

create table TEACHER_ACC (
	ID int identity(1,1) primary key,
	TEACHER_ID int not null,
	foreign key(TEACHER_ID) references TEACHER(ID)
)

using System;
using System.Collections.Generic;
using System.Data.SqlClient;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Test_DML
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                string connstr = @"data source=.\sqlexpress; initial catalog=TEST; integrated security=true";
                using (SqlConnection conn = new SqlConnection(connstr))
                {
                    conn.Open();

                    // insert teacher
                    string cmdstr = @"insert into TEACHER(NAME) values ('teacher1')";
                    SqlCommand cmd;
                    using (cmd = new SqlCommand(cmdstr, conn))
                    {
                        Console.WriteLine(cmd.ExecuteNonQuery() + " inserted");
                    }

                    // insert teacher_acc
                    cmdstr = @"insert into TEACHER_ACC(TEACHER_ID) values (1)";
                    using (cmd = new SqlCommand(cmdstr, conn))
                    {
                        Console.WriteLine(cmd.ExecuteNonQuery() + " inserted");
                    }

                    string selstr = @"select ID, TEACHER_ID from TEACHER_ACC";
                    using (cmd = new SqlCommand(selstr, conn))
                    {
                        SqlDataReader r = cmd.ExecuteReader();
                        while (r.Read())
                        {
                            Console.WriteLine(string.Format("{0} {1}", r[0], r[1]));
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex);
            }
        }
    }
}