I never did agree with the draft - aside from filling the ranks with people who didn’t want to be there, it is my opinion that 18 is to young to be in combat.
Certainly I do not agree with high school kids voting.
Never did, even when I was a teen in the 60s & early 70s.
If recruitment of teenagers is needed, then perhaps a tiered system would be better, where, except in cases of real emergency, you may not serve in combat units, but be relegated to other support duties with pay and benefits reflecting such.
In WWII the average age in the military was higher - in the mid 25s I believe.
Returning the voting age to 21 would, at least, improve the maturity of the average voter...