Dummy variables in logistic regression models

Why do switching of values in a dummy variable and the use of class statement in PROC LOGISTIC change the coefficients in logistic regression?

(1) and (2) produce the same results. (3) and (4) produce the same results.

(1)
proc logistic data=here.asdf descending ;
model college= boy ;
run;

(2)
proc logistic data=here.asdf descending ;
class girl;
model college= girl ;
run;

(3)
proc logistic data=here.asdf descending ;
model college= girl;
run;

(4)
proc logistic data=here.asdf descending ;
class boy;
model college= boy ;
run;