In my database there are 3 options that can be ticked contained in one field - school1 school2 and school3. One, two or three options could be ticked. How can I make a search so that on the find page, if 'school1' is ticked, results contain those with just school1 selected, school1 AND school2 (or 3) selected or all three? At the moment a search like this only yields results that match the query eg just school1 ticked.

Is this possible with all 3 options in the same field of should i make 3 fields - one for each school?

Let me confirm: you have a field "School" whose data entry option is formatted as a checkbox and the value list attached is School1, School2, and School3. Therefore, a user could select none, or any combination of the three.

If this is so, a Find screen with the same field formatted as a checkbox should perform the find just as you want. It will find any record that matches the selection in find (since the record is actually storing the schools selected in the one field, separated by carriage returns).