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Chances are you cannot do much about it in the short term. However, if it is an important keyword for your campaign, you may want to create a separate ad group for it. In that case, you may create an ad copy within that separate ad group that is highly relevant to the keyword. Try to make sure the keyword comes up once in the ad headline and once in the description lines. Also make sure that the new ad copy links to a highly relevant Landing Page. Such practices will over time improve your Quality Score and subsequently you may be confident that the ad will show more frequently.
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The main reason behind this probably has to do with your keyword having low QS. If this is the case, be sure your ads and landing pages relate closely to your keyword. If you believe these are fine, bidding may also be an option - this will place you on a better position and will increase your chances of good IS.
In either case, if "Guardians" is your main keyword, consider creating a new ad group with [Guardians] in exact match. Single keywords are often the cause of unwanted traffic resulting from irrelevant search terms (the word 'guardians' may appear in thousands of combinations and there's a big chance the majority of them will have nothing to do with your business).
You can also go through your search term report and choose your top search terms as the base of one or more new ad groups.
Hope this helps. Good luck!
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Just to add to @Boryana and @Lakatos I would certainly monitor very closely the search terms for this keyword and pay close attention to adding negative keywords. I have seen similar accounts and almost always single phrase keywords with multiple meanings picks up a lot of irrelevant traffic. It is definitely in my opinion adding the exact match and also some variations of "guardians", for example [high school guardians] or [home school guardians] (just guessing here some examples) and tailoring the landing pages to make sure they reflect accurately the search term - obviously this is a lot easier to do with exact match types as you know exactly what the search term is.
I worked on a similar account where a client wanted to bid on keywords nothing to do with their business, but felt the type of people using those search terms would be likely to convert. Naturally, the QS when i took over was 1/10 and rarely shown. I found that by building out the ad groups as suggested and creating some landing pages around these search terms gradually helped the QS creep back up to a satisfactory if not spectacular score.
It is also a really good idea to monitor Quality Score in a structured way. Personally I like to do this via scripts which runs every day. This way you can keep a really good check of the changes you make and the impacts they have over time (which can often be easy to forget). If you need more info on this just post me back and i will paste a shared QS script solution with easy steps to implement.
Really best of luck