Hello Saro,
To get the good goverment college in tamil nadu, for sc category is atleast 150 marks in Tamil nadu entrance exam (TNEA).All the government colleges give admission for engineering on the basis of marks obtained in TNEA exam which is conducted by Anna University. Also it depends with specialization and Anna university campus which you are choosing. Usually alAnna University chennai campus is filled first ,followed by rest of the campus of Anna University like Coimbatore,Trichy,Ariyalur etc.