Edit: See also the PDF linked here:
Wikipedia has a list of mathematics education journals; I happen to prefer the list of mathematics education journals compiled here, as they are provided along with some basic facts: journal summary, type of articles solicited, audience reached, etc. Some of these facts derive from the following article:
Törner, G., & Arzarello, F. (2012). Grading mathematics education research journals. Editorial: Reminiszenzen, pp. 31-34. Link (no pay wall).
The second link includes journals that are of generally higher repute in the field of mathematics education. So, for example, although the journal you mention in the OP can be found at the first link (without its own wikipage) and is graded with a B in the Törner and Arzarello article, it is missing from the second link; so, I might be hesitant about targeting it as a destination for publishing. I know that it has published a couple of questionable articles in the past.
My advice would be to look through recent issues of some of the journals linked to above (assuming you can access them, e.g., at a library or an academic institution), and see where you can find pieces that resemble the sort of paper you would like to write. You may also wish to look at where/if they were cited later on, or at the relevant journal's impact factor/circulation.
One example of a journal that is practice-oriented is NCTM's Mathematics Teacher, which includes a section specifically around mathematical findings called Delving Deeper. A description of the journal can be found in the second link above (click through for larger print, or check link):
The appropriate destination will depend on the level of the mathematics discussed (both in content and in the language that you use) as well as your ability to ensure that it is not just mathematical findings of too low a caliber to include in a journal of mathematics, but rather that it is connected to "practical mathematical teaching" in a manner that you can describe, justify, and link to the literature on mathematics education.