Changed: Content*s*, missing quote in format, BMI not specified in Tabulate, missing RUN boundaries, unneeded quit.

title Height, Weight, and BMI;
title2 by Sex and Age Group;

proc contents data = SASHelp.Class;
run;

data BMI;
set SASHelp.Class;
Height_m = Height * 0.0254;
Weight_kg = Weight * 0.4536;
BMI = Weight_kg / Height_m**2;
run;

proc format;
value $Sex 'M' = 'Boys'
'F' = 'Girls';
value AgeGp 11-12 = 'Preteens'
13-16 = 'Teens';
run;

proc tabulate data=BMI;
class Sex Age;
var Height_m Weight_kg BMI;
tables (Height_m Weight_kg BMI)*MEAN, Sex Age ALL;
format Sex $Sex. Age AgeGp.;
run;