There it is, the standard "missed the start of the year and now you're Invisible Man"
Can confirm that it does indeed happen, even if not really in the way it usually does in manga. Oftentimes it's half-self-inflicted. You don't
feel like you can fit in, so you make less attempts to, even if the rest are perfectly willing to let you in. I've been on both sides of that, and 3 times out of 4 that really went away after a month. The 1 out of 4 guy just dropped out two weeks after transferring.
Then again, that was in university with smaller groups and more mature people, not highschool teenagers, so it might be different.