Looking thru several sites the cadets most likely would have been armed with M-14 rifles and Colt pistols along with whatever they could liberate from local gunstores.
Most likely, considering who their teachers were, they would have also had improvised explosive devices and mines using dynamite and explosives cooked up in the chemistry lab, which definitely would have slowed the Mexican's down and cost them armored vehicles in the process (and could explain why they blasted them out with artillery - i.e. they lost too many armored cars and APC's to mines and IED's and good old fashioned Molotov's trying to storm their positions or fix the main roads and decided they had spent enough time screwing around against a bunch of kids)
also given how exposed the Academy itself (its at the airport and is wide open to an armored assault) and how far it is from the roads they were trying to deny to the Mexicans, they probably didnt make their stand at the actual Academy. Instead they probably used buried explosives to crater the main roads and force the Mexicans to go thru the town so they couldnt bypass the town's defenders and thus give them cover and a chance against the armored vehicles and heavier weapons the Mexicans had
|