My boyfriend is actin different ever since skool started?

me and my b/f been datin 4 2 1/2 months now and our summer has been great but now i think ever since we've been at skool hes been actin different i think hes advodin me at skool but on the weekends we act like its da summer all over again so what is it is he avodin meor is he jus followin skool rules and not tryin 2 get in trouble