Who to ask for letter of rec

[moyru]

I'm wondering who I should ask for my letters of rec.

 

I'm applying to Harvard's Technology, Innovation, and Education masters program.

 

I've been working at the same district for a little over 2 years (now going on my third year), but each year has been a different school. I have asked my former principal and one of my good colleagues to write me a letter of rec.

 

I chose a former principal over my current one because I felt my former principal would be able to say more about my performance/potential as an educator simply because I worked there longer. I've only been at my current school for a few months (since this school year started).

 

Should I also ask my current principal to fill out a letter of rec?

 

The other alternatives are a professor from a masters program I recently completed (but we didn't really develop as close of a relationship) or one of my teaching mentors. I could also ask one of my professors from one of my undergrad courses, but I wasn't sure if my letters of rec should be from someone I've worked with more recently.

 

Any suggestions?