The first thing you need to be aware of is why you want to do a survey. What kind of results are you hoping for? How are you going to use the results? It is extremely worthwhile discussing these questions and writing them down as a guideline for further development of the questionnaire.
Main strategic focuses of a survey could be:
Needs assessment. A needs assessment which will function as a basis for developing a project or method. A typical needs assessment could include some questions about knowledge, attitudes and behaviors, but should focus on expressed needs and challenges of the target populations, like students, teachers and principals.
Empowerment. A specific form of needs assessment is an assessment focusing on empowerment of the target group itself. In this case, LGBT and questioning students could be such a group. The best way to start empowering target groups is to involve them from the start in the assessment. This can be done by already involving some students in the construction of the survey, but also by involving them in implementing it. In such 'empowering' research, it is better to use open-ended questions and encourage open dialogue and involvement. It could be a kind of action research which recruits respondents to become activists.
Baseline monitor. A baseline monitor measures key indicators for the social inclusion or exclusion of LGBTG people. Such an instrument preferably also looks at related general related indicators, because homophobia and transphobia are commonly not acted out in isolation but are aspects of a more general intolerant and unsafe social climate.
Evaluation. A pre- and/or post measurement of the situation in a school, or regionally, with the aim to develop or evaluate a project which improves the safety in school. Such an instrument will focus on concrete knowledge, attitudes and behaviors that you are going to change. It is only possible to develop an instrument like this after an analysis of potential objectives. An evaluation instrument may contain similar questions as a baseline monitor but will also add specific questions related to the project or method that will be evaluated.
Advocacy. You may want to use the results of the survey to make schools, administrators and politicians aware of challenges. In this case, the questions should be selected in such a way, that the results yield high percentages of intolerance, because high percentages will have a high impact in the media. For example, a question like "Have you ever heard someonecalling someone else faggot?", will yield higher percentages then "Have you been called faggot in the past month?". Open questions about bad experiences (so-called "black books") are also useful in surveys for advocacy.
Combining two or more of these aims is always possible, but creates several difficulties. Some aims for surveys require a sound academic and independent research design, while others require a high level of involvement of target groups. These may not be easy to combine. Also, a combination of aims and methodologies may require a long list of questions. The longer the list, the more time it takes to be answered and the more difficult it becomes to implement it in schools. Schools are often very busy and giving up teaching time to research is usually not their priority. Critical choices need to be made here.
There is a long standing debate about how "homosexuality" and "gender" should be defined, and as a consequence, how "homophobia", "transphobia", "homonegativity" and "heteronormativity" should be defined and measured.
A main distinction is to measure knowledge, attitudes, skills and behavior. Good question batteries (core sets of questions that have been show to really measure what they intend to) therefore ask:
Knowledge: what students or teachers know about sexual orientation and gender identity, and to what extent their information is distorted
Attitudes: what students or teacher think about sexual orientation and gender identity, and how negative or positive these are
Behavior: to what extent students or teacher behave in a positive or negative ways towards LGBT or non role-conforming people
Researchers from the U.S.A. have taken the lead in developing questionnaires to measure homophobia. Examples of such question batteries or scales are:
Hudson & Rickets: Index of Homophobia (IHP), 1980 (25 statements)
Homophobia has consistently be shown to be aligned with other forms of intolerance and predictors or intolerance. Therefore, "homophobia" scales are often accompanied with scales which have show to measure these other predictors adequately. Examples are:
Levinson & Huffman: Traditional Family Ideology Scale (TFI), 1955
Troldahl & Powell: Dogmatism Scale, 1965
MacDonald: Ambiguity Tolerance Scale, 1970
Most of the questionnaires on homophobia offer statements to which respondents have to agree or disagree on a 5 point scale. Many of the statements represent rather extreme prejudices. The consequence of this is that some of these scales maybe be reliable in highly homophobic populations, but much less in populations where it is politically correct not to discriminate. As yet, there are few reliable scales which measure homophobia or heteronormativity in rather tolerant but not necessarily accepting populations.
In more recent years, more advanced sets of questions have been developed. Most notably, the availability of fast computers has made it possible to develop new and very refined tests that measure implicit prejudiced feelings and attitudes: the Implicit Association Test (see: https://implicit.harvard.edu/implicit/). The problem with these test is that they are still difficult to implement in schools (you need online computers for every student). There have been some attempts to create paper version questionnaires that try to emulate the refinement of Implicit Association Tests (see for example Chris Parker, 2003).