There are two basic ways to increase the overall probability of getting accepted to at least one school in a list: a.) include a safety of 95%+ odds; b.) increase the total number of schools in the list.
In a typical list of 6 schools with a safety, if you replace the safety with low matches, you need ~9 schools total to equalize the odds (i.e. the safety is worth ~4 low matches). That’s why it’s dangerous to not include a safety: many students who replace the safety make the mistake of not using “low matches” for the replacement, and not using enough of them. These are the students who end up pitching a shutout. They start out by grossly overestimating their odds for each school on their list, then compound that error by either not having a safety or not having enough schools of sufficient probability to replace the safety.
It’s possible to achieve a 99%+ overall probability of getting accepted to at least one school by having a list comprised of 7 “coin toss” schools. However, that strategy can be catastrophic if the actual odds for each school are far less than the estimated odds. Overestimating odds in this game is really easy to do because the task is difficult and more time-consuming than most people bargain for, plus most kids and parents are naturally so full of hope.
At the end of the day, the most expedient and “safest” way to ratchet up the overall probability of getting accepted to at least one school is to include a safety of 95%+. With a safety, 6 total schools of varying odds will suffice, providing the odds are estimated conservatively. If you add a couple of “coin toss” schools for good measure, your overall odds should increase to 99%+. Voila, no gap years on the French Riviera or bagging groceries at the Piggly Wiggly!