As a result the 20-year-oldwill now be suspended for the Bees' matches at home to Exeter City in the Johnstone's Paint Trophy and away to Oldham in League One.
The Bees slowly settled and MacDonald headed over before the home side had shouts for a penalty waved away after Diniyar Bilyaletdinov ran into the back of Myles Weston.
But the Bees defence was finally breached as Van der Gun headed home Serra's right-wing cross from close range, following good work from Joe Allen in midfield.
Its boosters argue that one-on-one instruction helps children learn, and point to the striking number of home-schooled children who win debating contests and spelling bees.
It may be extreme to say the Gee-Bees are hurting the rest of their generation, but indie record labels, home to most of today's worthy music, do not aggressively market new sounds to boomers.
Ritchie Humphries and Adam Boyd hassled and harassed the Brentford defence and Chris Westwood flashed a header wide as the home side increased the pressure towards the end, but they could not find a way through the Bees defence.