Bell do some good cycle / skate helmets for kids, they have fairly decent all round the head protection and come with extra foam inserts for size adjustment. Also as an added bonus they have some fairly cool designs and they wont break the bank.
My lad has had his best part of 3 years now and I would buy one again without hesitation.
Yep these, Bell Fraction for smaller kids and Bell Faction for bigger kids. There are 3 different thickness of pads for both front and back of the lid so you can easily get them to fit very snug which seems better than the normal rear ratchet IME. Also they look cool as but unfortunately you look like you’re on day release if you try and wear one as an adult.