My 6-year-old is under 40 pounds and sti

Yes — keeping a 6-year-old under 40 lb in the forward-facing 5-point harness is the right call. What decides the switch is the seat's own height and weight limit for the harness, not the birthday and not what other families do. Under 40 lb is not, by itself, a reason to move up.

1. What you already tried vs. the better lever

You tried moving to a booster because of age and peer pressure, and you landed on the correct rule (keep the harness to the seat's limits) — that instinct was right. The better use of this week is not deciding *when* but checking three things that decide everything:

• Read the label on the seat itself (2 minutes). Harness height limit and weight limit for the harness mode, the manufacture/expiration date sticker, and the model number. Those three lines are the whole answer to "when." The child's height matters as much as weight — many of these seats are limited by standing height or by head position, not by the pound.
• Check the seat for recalls and check its history (5 minutes). The model number goes into the official recall search on the national road-safety agency site for your country. Any crash history, even a minor one, means the seat should not go back in the car until a certified child passenger safety technician has inspected it.
• Book a free seat check (20 minutes, once, then it's done). Certified technicians do these at fire stations, hospitals, clinics, and police stations, usually free, and they check the install, the harness height, the expiry and the fit — so you stop guessing.

2. Constraints and avoid list

• Don't buy a booster "in advance" for a child still inside harness limits. If you end up shopping later, wait for the fit test below to say yes, and buy the belt-positioning booster (raises the child so the vehicle's own 3-point belt sits correctly) — never a booster-only backless style that relies on the lap belt alone.
• Never move a forward-facing child to a booster because the straps are uncomfortable. Straps above the shoulder in forward-facing mode are the fit telling you the harness is outgrown; that's a "check the label / see a technician" signal, not a shrug-it-off.
• Don't route the shoulder belt behind your child's back or under the arm on a booster — the belt goes across the shoulder and chest, lap belt low across the upper thighs. A lap-belt-only setup is not acceptable.
• Back seat only, and not the middle of a front seat with an air bag. Local rules vary; the technician will tell you what applies where you live.
• Keep the harness snug, chest clip at armpit level, no bulky winter coat under it, top tether anchored. Re-check the install after a few minutes of driving.
• If your child vomits, chokes or has breathing trouble in the car, the harness comes off first — loosen it and treat the child, then reinstall. Never wrestle the straps with a struggling child.
• The seat's expiry date and recall status are not opinions. Expired or recalled = don't use it; that's the one hard stop in this whole answer.

3. Decision tree — screenshot this

```
Is the child still within the seat's HARNESS height + weight limits (label)?
├─ YES → Stay in the harness. Nothing to change today.
│ Book the free seat check when convenient.
└─ NO (or head level with / above the top of the seat)
→ Belt-positioning booster, back seat, lap + shoulder belt only.
Then check readiness to drop the booster:
1. Back fully against the seat, sitting upright the whole ride
2. Knees bend at the edge of the seat, feet flat on the floor
3. Lap belt low and snug across the upper thighs, not the stomach
4. Shoulder belt snug across shoulder and chest, never under arm/behind back
5. Can stay like that for the whole ride, not just the first 5 minutes
All 5 yes → seat belt alone. Any no → keep the booster.
```

Red flags — stop doing it yourself and get help

• The seat is past its expiry date, has been recalled, was in a crash, or you don't know its history.
• In forward-facing mode the harness straps sit above the shoulders, or the child's head is at the top of the seat shell — that's the fit saying "outgrown," and a technician should size the next step.
• The seat moves more than about an inch at the belt path when you tug, or a strap is twisted or frayed.
• The child cannot stay properly positioned for the whole ride and keeps slouching or escaping the harness.
• Anything actually happening to your child's body — a breathing problem, an injury, a sudden illness in the car — is a medical question, not a seat question. Call your local emergency number and don't troubleshoot seating first.

Your 24 hours (about 25 minutes, one time this week)

Tonight: 2 minutes reading the label on the seat. Monday morning at drop-off: note the child's height on the fridge next to the school bag, and one check of the strap position before you close the door. This week: book the free seat check, and if your household is arguing about it, send the label line that says the switch date — the seat, not the birthday, ends the debate.

Success in 24 hours isn't a new seat. It's: you know the exact height/weight limit printed on your seat, the child is still correctly strapped in on Monday, the free check is booked, and everyone in the house is quoting the label instead of the age.

The script when someone else weighs in — "The seat says the harness is good until X. When we hit X, we move up, and a technician checks it first. Until then it stays." That's the whole conversation; it doesn't need defending twice.

I don't diagnose and I don't set a switch date for you — the seat's label and a certified technician's in-person check do. Tell me the model number and label limits and I'll tell you exactly where on the tree you stand today.