Best racing wheelset for junior club racers?

I would suggest talking to a custom wheelbuilder - DCR Wheels in the UK are amazing.

If you get a decent hubset then these can be built up again each time they are trashed/worn out or ready for a rim/spoke upgrade.

I guess what I would be concerned if my child was racing is the cost of stuff since the child is unable to work and pay for it themselves; in addition to that beginner racers, even CAT 3 not alone junior, have a lot of crashes which means a lot of damaged stuff and wheels tend to be the most damaged.

In light of that I would find cheap wheels, I would be insane to buy wheels costing $500 for junior racing, I don't care if some other junior is sprouting $2,000 wheels, if those parents want to throw away money then go at it but I don't play that game.  This is a child, we get no sponsors to shower us with money or wheels or bikes or whatever, I as a dad have to pay the whole tab so I'm going to go in as cheap as possible.

So what would I buy?  !st on the list would be Rodi Airline Evo, these cost $124 for the pair!  Fulcrum Racing 7 LG wheelset cost $184 for the set; of the Fulcrum Racing 5 LG disk wheel for $286.  Anyway here's a list of wheels you can get for under $400:  https://www.ribblecycles.co.uk/components/wheels-tyres/wheels/?dir=asc&o...

I use to race, I can't even count the number of times I saw people destroy rims, and I was racing with adults,  juniors? oh dear lord be prepared to pay, in fact buy two pairs of wheels because you're going to need a set in reserve.

Double like on What Simon E said. It's right on the money.  Participating not too seriously in a number of sports builds the best athletes.

By all means get him a lighter wheel set (the cool thing about young kids is they can ride silly light wheels) but I would strongly suggest sticking to alloy brake tracks, from my LBS who have taken a large number of youngsters through all the way from 11 yr olds to the pro ranks,  they say when kids stack the wheels seem to take the biggest hits, and alloy wheels are cheaper to repair and replace. A pair of Dura-ace C24s would be really really good . I can get them brand new in NZ for about 700 GBP, a pair of not knackered second hand should be about 400 - 500 GBP. Avoid the arms race, and buy sensible stuff that will go a few years. In a 10k crit his frame weight is going to be fairly immaterial.

And well done to the lad. 

I would disagree a decent pair of reasonably aero wheels won’t cost the earth, I wouldn’t go for high-end kit at this stage as in a few years your son will be able to tell you the exact feel and properties he want’s from a wheel set - that’s when things get expensive!

Perhaps these would be a good starting point? 

50mm: http://www.wiggle.co.uk/prime-rr-50-carbon-clincher-road-wheelset-1/

28mm: http://www.wiggle.co.uk/prime-rp-28-carbon-clincher-road-wheelset/

In the UK British Cycling's rules stipulate a maximum rim depth of 35mm. Check the rules set by your governing body before you spend any money. Slightly better wheels won't win races, though the promise of something lighter than the original wheelset might help his motivation and make the bike feel more rewarding to ride. But I would caution against spending too much at once, they could get trashed at the next crit.

Most importantly, at the age of 10 it must be fun - too many kids burn out by 15 or so and give up because the parents take it all too seriously. Over specialisation at an early age is similarly harmful. They need variety, developing a wide range of skills and disciplines, nothing even remotely serious until at least 14. The quote below explains one of former BC coach Tim Buckle's key concepts relating to youth coaching and development.

Quote:

Tim Buckle, a coach on the Olympic Talent Programme, describes how riders are developed using an analogy of a Snickers Bar. Skill (nuts), speed/neuro-muscular activation (nougat), technical and tactical knowledge (chocolate), bravery (caramel) and work ethic (the wrapper) are recognised as the constituent components that a rider needs to develop prior to them reaching the junior category at age 16.

Whilst competition is not neglected, learning is the main focus of the programmes. Coaches, riders and parents are encouraged to focus on the learning process rather than the outcome of competition. Physical development and winning come later.

I have digressed somewhat from the original question, I hope it is constructive.

Wheels could help but going up a level means looking more at tactics and sometimes accepting that early on it can take a little while to adapt. 

IMO deep aero wheels over a 6 mile crit race is not going to have the impact you think but even if placebo still worth getting. I would go 38mm max depth rear and max 32mm front. Easton make a lower profile carbon tubular wheelset, I have some, very light, sub 1800g incl tyres, also upgrade tyres.

Example of pricing, second user wheels sub £500 for mint condition on ebay k, £500 for new rear http://www.wiggle.co.uk/easton-ec90-sl-rear-road-wheel-tubular/?lang=en&...

I would recommend talking with custom wheelbuilders for their suggestions on matching rims/hubs/spokes with each other that are in your budget range - be it clincher, clincher tubeless ready, or tubeless rims. Be sure to leave room for a good set of rubbers.