If you're after Gymnasticats, Family Gymnastics, Girls Level 1, Tumbling for 3's, or popular adult fitness slots like Body Sculpting at Langston Brown — you need to be on the page and ready before noon ET on registration day. Pottery, science, most sports leagues, and martial arts can be registered for the next morning.
If you only read one thing
Be on the registration page before noon ET, not at noon — the virtual queue can put you minutes behind. Gymnastics for ages 3–6 and Saturday-morning swim slots sell out in seconds. Ceramics, music, and most sports leagues sit open for weeks — safe to register at leisure.
Total bar height = % of category sections sold out. Look past the red Instant segment to see the differentiator: gymnastics has a long tail of 6–24-hour sellouts, while tennis and adult fitness are almost entirely instant-or-not.
By day of week
Total bar height = % sold out that day. A tall red-dominated bar means highly competitive (gone in minutes); a tall blue-dominated bar means still sold out, but you had hours or days to react.
By time of day — weekday vs. weekend
Two stacks per time slot: left = weekday (Mon–Fri), right = weekend (Sat/Sun). Stack height = % sold out. Solid fill = weekday, diagonal stripes = weekend.
Weekday (Mon–Fri)Weekend (Sat/Sun)
By age group
Bar length = % sold out per age bucket. Segments show the speed distribution.
By location
Top 12 facilities by sellout rate (minimum 3 classes offered). Bar length = % sold out; segments = speed bins.
Practical tips
Day-of strategy
Be on the registration page well before noon ET — not at noon. Arlington uses a virtual queue: at the moment registration opens, the system hands every person watching a waitlist number and only lets you proceed when your number is called. Depending on traffic that can take seconds or several minutes. The competitive sections (red segments in the charts above) sell out inside the first 20 minutes, so a slow draw means you can be admitted only to find your target already full. Have the activity code copied so you can jump straight to it the moment you're in.
Where the real competition is
Gymnastics at Barcroft = hardest target. Sections for ages 3 to 6 (Tumbling for 3's, Gymnasticats, Family Gymnastics, Girls Level 1) are the most contested. If you're after one of these, treat the queue tip above as non-optional.
Long Bridge swim Levels 1–4 are very competitive but spots open across many time slots. If your first-choice time fills, pivot fast — sister sessions at less-popular times (mid-afternoon weekdays) often still have room hours later.
Weekend morning slots (Saturday 8:30–11:30am) are the single most competitive time-and-day combo. If a weekday afternoon slot works for you, you'll face dramatically less competition.
Adult fitness has a few sleeper hits. Body Sculpting, Cardio Body Sculpting, and Barre at Langston Brown sold out in the first poll cycle. If you want a specific instructor or time, register on day one.
Where it isn't (safe to wait)
You probably don't need to rush for: ceramics, martial arts, music, science & discovery, sports leagues, arts & crafts, woodworking (with rare exceptions like "Intro to Woodshop"). These had near-zero sellouts in this window.
Every section that sold out instantly
Every section that was already gone by our first scan after registration opened — meaning the true sellout time is somewhere between 0 and ~20 minutes. The 20 min upper bound is a measurement ceiling, not a real number. Sortable; click any header.
About this data
Source: an automated monitor that polls Arlington County's public registration system on a schedule and records when each section transitions to waitlist or full. Sellouts faster than our polling resolution all collapse to the same bucket (the "Instant (<20 min)" bin is a measurement floor, not a real duration).