Your son probably aims better, but you can compensate this with moving and positioning smarter.
When playing use the map a lot and go to locations where there are already 1-2 teammates.
If you manage to help these small groups to win their fight, your team will snowball into victory

I believe the scoring is really "aim %" dependent. Like you (OP), I often get to the 1st half of the scoring board, circled by "silver" gamers upwards and downwards, but I still lie at level 1 (after 1400h lol).

I remember half a dozen years ago, I was stable in the Silver level because I did NOT full auto "air-shoot" to make repressive shootings - to slow a bunch of aliens incoming for example, making them think there is more than 1 player in the location they want to go, etc, to halt their progression few saving seconds and buffering the situation before "reinforcement".

And I did NOT rush like hell in a bunch of aliens (1 vs the world), to get a lucky kill and then die instantly.

And I did NOT full auto on a moving alien - I noticed, if you shoot the same amount of bullets by using several bursts of 5 bullets, you make more damages (maybe the netcode / hitbox is a bit flawed?), than auto-shooting the same moving alien - maybe some bullets get more easiliy lost in the netcode/lag/dunno why.

----> an example to illustrate this lag in the netcode >< hitbox:
- I shoot an alien until i'm almost dead (he bites me 2 times for example), near a phase gate.
- Almost dead, I jump prevently to get back to the main/armory/whatever.
- I die "EN ROUTE" whilst in the 0.5 second Phase "flux" and my weapon (example: a flamethrower or GL), is dropped at the other side of the phase gate, as my corpse. At least 500 milliseconds of delay while my ping is at 17ms.

SOOOooooo, yeah, there might be some optimization to be made about the code regarding latency between a shot/bite and when the player receive the said shot/bite. So, that's maybe why shooting small bursts instead of full-spreading might get the code recording the burst better on a target. Idk, but it seems to be quite the feeling of it after 1400h playing and testing different ways of shooting etc.

(NOTA: just don't care about the ELO system, unless you want to comm... if you comm, then you'll have all the rage and fury of your team mates thinking you are a noob and can't comm just because of this silly level system). Don't worry, the community of around 120 daily players begins to know there is no need frightening low level players because, well, there won't be much ppl to play with if not...)