I've moved a lot of times in my life so a lot of my EC's are low tiers. I really believe that if I had the chance to stay at a school for more than two years I could have had some leadership positions. Right now I'm a junior at a new school and don't have many high tier worthy but I really want to seem like a competitive applicant for merit scholarships. Should I explain all this in my application essay? Is there really anything I can do to remedy this? Would an admission counselor read this and think it's an excuse or are they usually understanding with this type of thing?
I would not explain this in our essay. They will see on your record that you've moved and would understand. Your essay is one of your chances to cross this gap with superb writing telling a story of personal growth and should not be used for excuses or logistics. You can talk about how you have moved a lot, but the focus should not be how it hurt your college application, but how it hurt you and -most importantly- what you did to overcome it.
Try getting involved in some community service. Do something that lasts the whole summer and help the people around you in that way. You could also go to a college preparatory program or workshop in the summer.
Yes as a junior myself I know how it can feel when you are limited in having positions or just joining ECs. In the college applications, there should be a section where you can add this at the very end of your application and just tell them how you keep switching schools that way colleges are more aware of your situation. They will also see it in your transcript. Hope this helps.
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Yass! I feel like lots of people get caught up in writing about a setback. Frequently they forget to elaborate on how it was overcome, which is the most important part as it shows them how you deal setbacks which in turn can tell them about how you are as a person.