How to Get Max Values from MySql

hello friends,

i have one problem actually i want to take Maximum values from one Column but this column data type is Varchar so its not getting values... do u have any idea how can get the Max varchar Data type values in Column... if yes then please let me know
i m also using this Quary but its not working "Select MAX (Columns) From t_student;

thanks in Advance
Naim Khan