To practice more efficiently, make a schedule of what you need to work on during the week. Write down when you will practice which piece, etude or technical exercise and for how long and stick to your plan.
You will be more efficient if you play only one thing per practice session and do it really well than if you put everything in the same basket without any organization. It will allow you to focus on one particular piece and to work on it more thoroughly. In the following practice session, do something completely different to work on a different aspect of your playing and to avoid stiffness from repeating the same movement too much.
Adjust the length of your practice sessions according to what you will be practicing. Don't try to work on worn out chops. Nothing good will come out of that. Allow enough time for your lips to recover between practice sessions.
I personally do 30-40 minutes on one thing followed by a 40 minutes break. Then I do another 30-40 minutes etc.
I know it's not always easy to get a practice room in a conservatory so you'll have to do with the time you have. Consider that factor when you plan your week.
I am associate principal horn of the Singapore Symphony Orchestra and the author of the progressive methods. I'm happy to share my experience as a horn player and teacher with you.