Is this sentence grammatically correct? If you can improve it, please rewrite it below. Thanks?

It is not a sentence. As a bullet point, it is acceptable. They are not sentences but sentence fragments, often avoiding the subject ("I").

Improved learning outcomes by effectively communicating with specialist teacher who monitored progress.

"This student was frequently in contact with a specialist teacher, who kept an eye on the student's progress. This contact was seen to be good for the student, who made good progress in their studies."

This is not a sentence as it does not have a subject. Add an I before regularly.

What is the context? Did YOU communicate? Or is there a possibility for regular communication?

It would be better if written in a less formal tone. I understand what you are writing, though I think that its mostly jargon.