Attendence System using Face Recommendation

Any face recognition api can be used
Teacher will be able to make different classes section, in which Attendence will be taken for different students using face recognition. When class ends the attendence will be automatically be send to respective teacher, if attendence of any student in any subject fell below 75%, website should automatically send mail to the student.
while taking attendence , if camera fails to recognise student then, their must be some alternate way to record attendence...and if it is used teacher must know who used it. if attendence fell short then 10% in class it must be included in mass bunk.