Regents is very different and a little bit dumbed down compared to what they're teaching in most other states. The heavy reliance on reference tables, the multiple choice testing format, and the highly reductionist content is of completely local invention, making it necessary for NY state students to check and see if there is a gap in how they learned chemistry and how it is taught on a national scale.
A student who is keeping up fine with their Regents Chem course could self-study this difference by looking at an extra textbook throughout the year, making sure they know electron orbitals, titration, acid base neutralization, formal charge, electrochemistry, balancing redox reactions, kinetics, equilibrium, etcetera, in the same way that the SAT test covers it.
This can be done by a reasonably well disciplined student on their own. It can also be done with a tutor. What I have done in the past is work with a student from a supplementary text throughout the year, backing up and amplifying the normal lessons they are getting from each chapter.
You can also call me around late February or over vacation weeks to do some one or two hour sessions where we just go through a Sparks Notes, Barrons Review Guide or similar.
I don't have any requirement for minimum number of lessons. Sometimes high school students just get a couple weeks at the last minute, like in May. It's not ideal but it does seem to help and make everything feel more consolidated in their mind.