E-mail get's sorted as spam

Hello Guys!
(Sorry for writing in English, I just use English since my Danish is a bit poor)
I try to help out as a technical adviser at my children's school, a parent association school.
How ever the school has a email-service at a company that also host the website. Every week the teachers sends email to the parents, but nearly all emails seems to be sorted as trash/spam so a lot of email is never noticed by us parents. 
The company that provide the email service found out that one of there servers were black listed, but that should have been taken care of. Together with this company we have also created a spf-pointer. (I hardly know what that is or how it works)
Do you guys know any other precaution we can take?
Best regards
Fredrik