Locking seat belt on booster?

The lady I nanny for locks the seat belt on her kids booster seats to prevent them from leaning forward or moving the shoulder strap. Is this a bad practice? If so, why? I just don't think it' a good idea since it's not in the manufacturer instructions.

It's usually not bad practice, per se. In fact, it's something we often recommend when a younger child MUST be put in a booster.

However, ideally by the time children are in boosters, they're mature enough to understand that they have to sit properly without leaning out of position. There might be a transition period, but kids need to learn to sit correctly, and if they really can't, a high-weight harnessing seat would probably be a better answer.

Now, my Prius manual specifically says not to lock the seatbelt in booster mode. I don't know how many other cars have that same designation, but I would imagine not many.

It would seem intuitive that it would not be a problem (not that there is something I might be missing). In a collision the belt is going to lock in any event. Being prelocked in an ideal position would seem to be safest (a la race car drivers and 5-pt harnesses in child restraints). This is also the idea of pretensioners, they take up the slack in the first few fractions of a second during a crash to position a rider for the "ride-down" of the collision. Some cars have pretensioners in the rear, so prelocking in that case may not make a difference other than for the child that tries to get out of seat

There's nothing at all wrong with locking the seat belt, per se. Though I do agree with this:

However, ideally by the time children are in boosters, they're mature enough to understand that they have to sit properly without leaning out of position.

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That said, when my 7.5YO rides in a booster, he prefers (demands, actually ) to lock his seat belt and is irritated ifmhe can't.

Thanks! Your answers make sense. I just thought I might be missing something. If it is a good idea, why don't the instructions reccommend doing this all the time?

I was just wondering about this today as I have had to put children in boosters that their parents provided and the kids were clearly not ready, but it was an emergancy situation. I ended up locking the seatbelt on one child but I wondered if that was safer or what.

If you have no choice but to put a child in a booster who isn't ready for it, then locking the belt can help remind the child to sit properly.

something else to consider though. If the seatbelt is locked, and the child leans out of the shoulder belt, it could tighten firther, and the child would have to unbuckle to get back in. We had this problem with my 8 year old (who prefered to have it locked). SHe's not allowed to lock the belt anymore (and she's also not allowed to lean forward).

I know you got the answer already, but I'm just going to add that, in my dh's car, I've just always locked the belts on the boys... not to prevent squirming, but because I worried about the lapbelt being so easily loosened. If it weren't as snug as it is in my van, where the belts lock at the latchplate, I worried that just from moving their legs, the belt might loosen and, in a crash, that little bit of extra slack might let my child submarine out.

I have not thought of an age where I'd be fine not locking them only because, with my oldest now out of a booster, my boys now lock the belts on themselves without any reminder. It is habit and has been drilled into them just because it's what we've always done.

My 7yr old has actually complained that the shoulderbelts in my van don't lock, because he likes how secure the locking belt makes him feel.

I had to explain to them why we do it in that car and why my van's belts are still safe, and my concerns about the lapbelt being allowed to move and now he's fine again with my van.

I honestly will never give my kids the options to go without locking the belt.

Instead, as they get older and go with others, I will teach them how to identify belts that have locking retractors so that they can know when to lock them and when not to.

By giving them that power, I think it will prevent them from drawing attention to themselves doing it and thereby avoid any teasing from kids who don't lock their belts.