I will disagree as well with the above comment.
Biochem was not mentioned as something the student took or hadn't taken o I didn't take that into consideration in my advice.
Physics II and Orgo II by April - you will literally have a topic or two at maximum to cover from each subject category in most universities (as most universities end early May, and have finals the week before). In a 30 week sequence of each subject and most mcat books breaking these down into 12 chapters at maximum - that means you have roughly 3/30 weeks of learning or a 10th or 1-2 chapters of material from each subject you will have to self learn. The later Orgo II topics in university are not covered by MCAT organic chemistry either so you're actually going to be covering a maximum of 3 chapters on your own, which is a very easy task.
The benefit of having your MCAT with a score by May so you can apply when the application opens with no stress on June 1 is immense. If the student is planning so far ahead - he or she should have no issues finding some prep resources/free videos to cover the few topics ahead of time that he won't be covering in the MCAT.
Many students are taking the MCAT during their last few prerequisites as fitting in Biochem, Organic I/II, Physics I/II, G Chem I/II, Bio I/II, Psychology, Sociology, and additional classes (physiology or Anatomy & Physiology, Cell Bio, Genetics, Microbio, statistics, Biochem II, and a Reasoning/Ethics class which are sometimes floated as additional prerequisites that are useful for the MCAT) is very difficult to fit in in all before April of your Junior year for most students.
The student is starting to think about the MCAT now. He can get most of his content review done this summer for classes or Fall 2019 (lightly) , self learn topics for Orgo II/Physics II lightly (really not an emphasis on the MCAT) and then focus on practice materials/tests for his spring 2020 semester. If the student is graduating in 2021 - and does not want a gap year - he should really aim for a April test date or one in May shortly after graduation at latest if he can help it. Being early in the App cycle is tremendously advantageous - and although you can submit an application June 1 without an MCAT score - you're stuck in a limbo of not knowing your score and hence not knowing exactly where you'd be competitive for.
I agree with the poster that Biochem is super important - but I am unsure if the student has taken Biochem yet or not and/or when he plans to take it. I would try to take Biochem F19 if possible if the student is graduating in May 2021 (even though it would most likely be concurrent with Organic Chemistry). As a student who scored A-'s in both Ochem and Biochem courses - I do not believe organic is required to do well in Biochem and some universities will let you override that prerequisite.
Regarding curves - No such thing. The MCAT is standardized and the difficulty does vary - but the "curve"/grading accounts for this.
If you are going to go the gap year route -
@JSReed has a reasonable timeline he outlined but my advice assumed the student was looking to apply when he said he wanted to apply as a fixed and non-negotiable.