Six-man England needed a last-minute winner from Christian Lewis-Pratt to ensure they finished day one of the Las Vegas Sevens unbeaten.
England, who had earlier beaten Brazil 29-5, were tied at 7-7 with Scotland when Dan Norton was sent-off for an alleged trip.
However despite being a man down, Lewis-Pratt scooted over for the decisive score to seal a 12-7 win.
Norton, who scored a hat-trick against Brazil and England's first against the auld enemy, was later cleared at a disciplinary hearing meaning he is free to play in the group decider against Kenya.
Kenya beat both Scotland and Brazil to join Wales, New Zealand, Samoa, Fiji and South Africa as the only unbeaten sides after day one.
Wales face a crunch game against South Africa, with both sides having beaten France and Uruguay in the pool - while New Zealand and Samoa clash with England and Kenya awaiting in the last eight.
The final pool games and quarter-finals will be played on Saturday, with the semi-finals and final on Sunday.