Would I be better off taking a PG year in another secondary school or even my own and applying in another year?
Good Question! For many, the option of a PG year has always been thought to be something necessary due to something missed during regular four year high school program. There are numerous reasons to take a PG year: extended illness, surgeries, injuries, family challenges, etc. Under certain circumstances, taking an extra year after graduation to gain more courses or strengthen preparedness for college is considered a wise choice. Even many foreign nationals who come to preparatory or boarding schools for the last two years of high school, often opt to take a PG to improve language skills and grades. Under these circumstances, all benefit from making this mature decision.
However, this option began to fall out a favor in the late 2000’s because so many were not taking the PG as a matter of maturity or even to recoup what was lost due to a challenge faced during school. Rather the choice was made to improve a GPA or gain a position of leadership on a team, which was not necessarily needed but thought to improve the odds of getting into a higher caliber college or university or to, in essence, stack the odds in the candidate’s favor. Unfortunately, as time passed, the volume of students opting for PG years began to increase exponentially. This dramatic rise led to the scrutiny of such candidates and programs by colleges as to the effectiveness and appropriateness of this choice.
As colleges began seeing many of these candidates as less prepared with no increase in GPA during that PG year and sometimes even worsening of grades, admissions officers started speculating as to the effectiveness of such additional secondary education. Many began to think of this as a strategy to garner favor for admission, which would have been denied. Further more than a few of these less than optimal PG candidates were not adjusting so well in the first year of college, which only fueled the thoughts that these students were not prepared for college at all.. So the allure of the PG candidate began to fade….suddenly, the mature decision became tarnished. 
Does this mean a PG year is a weakness? Not necessarily, circumstances that explain why the PG year was necessary will always be taken under advisement, but I want to make it clear, having a PG year on a transcript will open the door for explanation. Certainly, an optional additional essay on the application is warranted. This is exactly why there is an additional essay option on most applications. Any usual experiences in a normal high school progression should be thoughtfully disclosed in such an essay. Admissions wants to understand and offer the benefit of the doubt to all potential students to their schools. Colleges will always help a students who need such consideration.
If you are going to go PG simply because you do not feel you can compete with your current classmates and get into the college you want, you might think this through. The choice to extend high school to increase your odds of a certain college might end up blowing up in your face. I would offer that you have much better odds, going to college, proving yourself in college and transferring into a program that is something more in line with your own personal vision. Transferring into a college with very good college grades is a selling advantage right away, because you are showing the desire to rise to a challenge and be dedicated to your own goal. All colleges want students who want a challenge.
If you are still unclear, you can always contact me for some more personal discussion.