I want to create two new dummy variables that say whether the variables primset and primact vary within classroomid. How would I do this?

For example, I want the new variable primset_var=0 because the values do not vary for classroom 101, but primset_var=1 for classroom 201 because the values do vary.

Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input int classroomid float(primset primact)
101 1 2
101 1 4
101 1 6
101 1 1
201 4 2
201 3 2
201 2 2
201 1 2
end
label values primset primset
label def primset 1 "1 = whole group", modify
label def primset 2 "2 = small group", modify
label def primset 3 "3 = free choice", modify
label def primset 5 "5 = meals", modify
label def primset 6 "6 = routine", modify
label values primact primact
label def primact 1 "1 = lit lang", modify
label def primact 2 "2 = math", modify
label def primact 3 "3 = science", modify
label def primact 4 "4 = social studies", modify
label def primact 5 "5 = art", modify
label def primact 6 "6 = other", modify