Joelle Renstrom, previous charter school teacher
Charter School waiting lists can be frustrating (ever seen Waiting for Superman?) The National Alliance for Public Charter schools estimates that there are roughly 163,000 students in NYC alone who are on charter school waiting lists. But the situation might not be quite as bad as it sounds. It's important to know where on the waiting list your child is, and how many students are typically admitted from the waiting list. This varies a lot based on the size of the school, the grade levels taught there, and the number of applicants. Each school runs its own lottery and admission and application procedures, so it's tough to generalize when it comes to advice. Are there parents you know who have been through the same process? Might they have advice for you? There are also people at the school who can give you more specific advice on best times to apply.
Often, waiting list numbers sound worse than they really are--many students apply to multiple charter schools, which drives those numbers up. It also depends on what grades the students are in. For example, I taught at a Boston charter school that had a lower school branch (5th and 6th grades), a middle school (7th and 8th grades), and a high school (9th-12th grades). The vast majority of applicants were incoming 5th graders; there were very few 6th grade applicants, and very few spots for them. But then there were more incoming 9th grade applications, too, as some students decide to go elsewhere for high school.
It's impossible to predict whether you'd fare better in another lottery next year, though it can't hurt to try. Charters do give preference to siblings of current students, and some give preference for other factors such as residence location or need. But every school is different. I don't know what grade your child is, but you could also considered applying again between elementary and middle school, or between middle and high school. And who knows--maybe you'll be pleasantly surprised by the level of education your child receives at a public school!