i am pretty sure that xxx has sufficient ability to carry on advanced study and research in xxx university. and he is able to assist teachers for their daily teaching and conduct research work for researchers in the lab.
i think through his hardworking efforts, he can make a successful career in the field of xxx science.
his english is good enough for communication. both oral and written ability is very excellent, so i believe he can cope with any possible problem in communication for the future. in a word, the basis of my general assessment is xxx is well-qualified for the graduate program of advanced study and research.
and i am glad to recommend him as an outstanding applicant to attend xxx university for his graduate study and research.