It's still best to have a fair percentage of relevant links, which can also be complementary interests, like a bow maker linking to an arrow maker site.
Back links from same niche has lot of power as they are your competitor links and getting back links from other webpages is also fine when they are coming from high PR sites with a do-follow attribute, these links will pass link juice thus helps in increasing your page rank.
Back links from relevant sites in your niche matters a lot. But other backlinks will also help you to some extent.
I'd say this is a difficult one to answer definitively. For example, if the back link was from a source writing about software, that may be relevant given the emerging influence/controversy re: educational software in the education sector.
However, that said there is talk about Google taking a more topic based approach and also emerging as an 'answer engine'. In this case, having your back links from 'on topic' sources should help to improve Google's perception of yours being an authority domain in that topic area.
Finally, also consider the quality/authority of the back links you already have in the 'blogging niche' - if they are low quality perhaps you might consider removing some of them, or at least countering them with some high quality on topic back links.
Backlink from your own niche matters a lot so try to make the backlink from your niche only!
I have an education blog . But I have so many backlinks from blogging niche . So will backlinks from other niches other than edu help me to increase my page rank and visibility in search engine...?
