Our system in High School was similar to this. Our Halfbacks (tailbacks) wore 20's, Fullbacks 30's and Wingback (H-back) wore 40's...the rest were the same. Except the school Superintendents son was a QB and he wore #7.
Since a lot of players played both ways the defensive numbering system was a bit messed up but it was supposed to be tackles 60’s or 70’s, DE’s 70’s or 80’s (you used to see 80’s on some DE’s in the Pros too), LB’s 50’s, DB’s 20’s 30’s or 40’s (any of the RB numbers).
When I was a kid you almost never saw a player with a number in the 90’s.