Is it correct to write "someone wants to focus on their study"?

Question

Here is the situation.

My colleague, T1000 recently quit his job as a shop assistant.
He is cool but nice. He was doing a part-time degree in a university.
He told us that his school assignment had become harder and heavier, so he wanted to quit the job.

Now, in my diary, I am writing this:

T1000 has quit the job so that he can focus on his school work and thesis.

I am not sure whether it is correct to write "someone wants to focus on their something"?

If it is not correct, can you suggest some other way of saying it?

Answer 1

Focus can take an object, answering the question who or what is being focused?. The typical preposition used with focus is on:

I focused the gun sight on the target.

If you don't specify an object, the "default" object is yourself.

I focused [myself] on my homework.

but if you leave out the on it sounds like what comes after is the object of the verb focus

I focused my homework { on ... what? }