which way is better for sending sms for school management system

Question

Hi friends
      I am creating a c#  windows  application  for school management system. in that i intended to send student daily attendance to their parents and occationally i want to send send sms for student,teacher,and office staff. for example student mark must sent after completion of exam. which way is better to send sms for this application. please refer me which one is better ?
                                                                Thank you in advance