The National Pesticide Information Center (see the link below) is a good source of information for this paper. As they point out, pesticides can not really be divided into "safe" and "dangerous." Instead, pesticides always pose a risk to humans and pets. The risk of pesticides depends on one's exposure to the pesticide and the toxicity of the pesticide.
There are several different options for this paper. One option is to write about methods of pest control that are less toxic. Another potential topic is how the Center for Disease Control (CDC) has developed plans to control pesticides in schools (see the CDC link below). They have developed a process called Integrated Pest Management to limit the exposure of children and teachers to pesticides. You could phrase your thesis along the lines of "The government should limit pesticides in schools to reduce exposure to toxic chemicals." The context is that children (and teachers) can show adverse health effects from exposure to pesticides. Then you want to include the pros and cons of your proposal, which depend on your research. In the case of Integrated Pest Management, the cons are that there could be extra costs from keeping up schools (for example, repairing cracks that are the points of entry for pests) and keeping schools clean to avoid pest infestations (part of Integrated Pest Management). The pros are that this proposal would reduce children's and teachers' exposure to dangerous chemicals and improve the safety of schools. In your paper, you can weigh the pros and cons of the plan and decide whether you think the pros outweigh the cons. Your conclusion can recap your proposal, stating it in different words.