Is Computer science branch is so tough if someone is average student?
S ee dear, It completely depends on your interest, if you really like coding and other technical stuff then it is going to be interesting for you but if you are not that interested in it then it becomes really tough for you.
Honestly speaking CS is such type of branch which requires a lot of efforts, brainstorming and patience from the student side. And it is a logical subject too which really requires brain work, so if you are ready to do these things then only go for CS.
And if you don't have much idea about what is there in CS, then goggle the syllabus of CS of your favorite college
and try to explore it or try doing coding if you like it, it's good and if not then give a 2nd thought to CS.
And at last, yes it is a bit tough if you look from an average student prospective.
All the best!!!