I would be very happy to provide a reference for Roy. I highly recommend him. My daughter started tutoring with Roy in the 9th grade and continued with him the next two years (10th & 11th grades). When she started she was taking the accelerated Math class and was having some troubles with her teacher's style of teaching. Roy was able to fill in the gaps for her and give her the confidence (and knowledge) to succeed in the class. In the first reporting period after she started tutoring with Roy, she brought her grade up from a B- to a B+. That may not seem like a big jump but she was in a very competitive class and the teacher was a hard grader, so she was thrilled.
After 9th grade, she continued to have the same teacher for the next two years and she also made it onto the Math Team (which the same teacher also led). Although she had by now gotten used to her teacher's way of teaching, Roy was extremely helpful in explaining some of the concepts more thoroughly and helping her when she was stuck with homework problems. He also helped her prepare for quizzes and major tests as well as the more complex math problems she had to face when competing on the math team. Roy was always patient and explained things to my daughter in a way she could understand. He also gave her different ways of thinking about solving a problem that she wasn't getting in class.
I asked her about the types of math she studied with Roy and it sounds like it ranged from topics in algebra (mass points, bases, etc.), trigonometry, and calculus. He sometimes used proofs to explain concepts to her. I doubt if there would be any math topic that he couldn't teach, however. He also suggested extra things for her to consider or learn and posed more challenging problems - she called them "enrichment problems." He not only was interested in helping her stay on top of her coursework, he was also trying to stretch her abilities. I think this really paid off for her - not only did she continue to do well in class, but she also got a perfect score on the SAT Math II Subject Test.
Hope you don't mind the long-winded review, but I wanted to show how important Roy's tutoring was to my daughter's success in math over the last 3 years. We usually met with him once a week during the school year and I believe his help really made a big impact on my daughter's ability. She also progressed from being insecure about her math abilities to feeling confident enough to tutor new math team members. In her words, she appreciated having a low pressure environment to learn math - a place where she wasn't been graded or judged, but just getting the personalized coaching she needed. She hasn't had to see him on a regular basis this year (she's taking AP Calculus) but will be using him to prep before big tests.
PS - I should also mention that Roy is a very nice person as well.