UISearchController に問題があります。tableViewに対して正しく配置できません。
結果のテーブルは、メイン テーブルの領域全体をカバーしていません。
resultsTableController = ScuoleSearchResultsTableController()
resultsTableController.tableView.delegate = self
searchController = UISearchController(searchResultsController: resultsTableController)
searchController.searchResultsUpdater = self
searchController.searchBar.sizeToFit()
tableView.tableHeaderView = searchController.searchBar
searchController.delegate = self
searchController.dimsBackgroundDuringPresentation = true // default is YES
searchController.searchBar.delegate = self // so we can monitor text changes + others
// Search is now just presenting a view controller. As such, normal view controller
// presentation semantics apply. Namely that presentation will walk up the view controller
// hierarchy until it finds the root view controller or one that defines a presentation context.
definesPresentationContext = true