[ If the teacher did not tell us [ to take all our books home on Friday ] ], 現在の反事実は過去形 who would take all his books home on a Friday? 誰が金曜日なのに本を全部持って帰るだろうか?持って帰りはしない。 反事実の話なので、過去形
[ because Friday is the day [ we get in the town and play after school ] ].