Since I'm a retired realtor and not knowledgeable with your area, I looked on Zillow to see what the problem is. Zillow has filters to see what homes have recently sold for. What I see the issue is unfortunately your budget is too low to buy a home. In zip code 21769 houses have recently sold in the $400 - 500,000. range and up. There are houses in the $300,000. but the square footage stated means the rooms are small. In this zip code it seems what you can afford is a town home or a condo - not a single family house. In zip code 21773, single family house prices are cheaper but still not low enough to buy a house at $300,000.
What I see happening is you need a reality check and you need to sacrifice. You need to decide what is more important - keeping your children in their current school district even if it means all you can afford is a condo or a townhouse OR moving your children to a different school district so you can afford to buy a single family house. My area in the suburbs of New York City is even worse where families are forced to sacrifice every day. Life isn't fair and I know it's a tough decision but unfortunately, the bottom line is you need to stick to what you can really afford - which is $300K not $350K. Do yourself and your family a huge favor. NEVER spend more than you are comfortable with. You will regret it later. If there ever is some kind of emergency or you need to come up with money for your children's whatever, where will you get the money from? You still need to pay your bills.
Bottom line - this is not Trulia's fault. Trulia is trying to tell you that there are no homes in your specified area that are within your budget.