Please find below videos on how to tie your school tie (right and left handed).
With your collar up, pick up the tie so that the wide end of your tie is held in the hand you write with. Place the tie across your lap, lift again using both hands, and wrap the tie round your collar. Ensure that the wide end is longer than the narrow end and that your tie is not twisted.
Lift the wide part of the tie in your writing hand and the other part with your other hand. Cross the wide part over the front of the narrow part and let the wide part go. Grasp the wide part from under the narrow part and wrap around once more and let it go.
Keeping hold of the narrow end, slip the wide end of the tie up and through the opening at your neck.
Let go of the narrow part, hold open the loop at the front of the knot and tuck the wide end of the tie down through the opening.
To tighten the knot up to the collar, hold the narrow end of the tie with one hand and the knot with the other hand and carefully pull down the narrow end and slide up the knot (use side to side movements if tie does not move easily).