Poor teamwork in sixth form - how to improve?

[RidiculousVehicle]

I started working at a new school this year and really like it, apart from one issue. I work with two colleagues (we are all sixth form specialists in a particular subject) and I share one set of classes with each of them e.g. all classes are shared between two out of the three of us. One colleague, I get on fine with despite a large age gap and very different styles. We have found productive ways to work together. The other, while we get on okay on a personal level, just doesn't want to share anything! I have let this person take the lead as the classes we share are year 13 so I didn't want to barge in and start changing predictions or altering things that were working well, especially regarding Oxbridge candidates.

However, some of the students give me quite a hard time and some have openly said that they don't like the units I'm teaching (I wasn't given any choice about which parts of the courses to teach and have definitely been saddled with the less engaging ones, although I'm trying to make them as interesting as they can be).

I don't feel this colleague has any respect for my skills or experience and there is little communication about what is happening in the other classes, no joint planning etc. I have tried talking about this to my line manager who has at least instituted weekly team meetings, but when I have asked what to do about improving communication (especially as colleague is part time so there are two days when we don't overlap), line manager says 'oh [colleague] isn't very technical, doesn't like to use email'. WTF?

As I am jointly responsible for the students' outcomes, I am a bit worried and also feeling really frustrated, as I managed to improve exam results a great deal at my last school so I know I have the right skillset if I were only allowed to use it. What can I do to improve things?