To send messages by Individual Student wise, follow the steps below:
Step 1:
        Click on home icon and select the Student Wall 
       module. Then, select the Student Wall (Chat) under the
        Student Wall menu.
Step 2:
        To have a one-on-one conversation with the student,
        you can click on Search Student option, or you can select
        the class and then select the student accordingly.
Step 3:
        If Search Student is selected, select the search field and then
        search the student or select the respective class & section on
        the left side then select the Message to Student Tab and 
        select the student accordingly.
Step 4:
       Write your comment accordingly and you can also send the 
       files or documents using the attachments icon. If you want 
       to convey the same message to multiple students, then tag 
       the students using the profile icon given then click on Send.
       Assignment can also be given to the selected student, by
       clicking on Give Assignment option.