My technician (secondary school D&T) bought a MAPP-oxygen torch with frame repairs in mind some years ago, but didn't have much success.
Don't recall any efforts to weld with it, just brazing - I think he was trying to flood a lugged joint and found the flame to be too localized, and then discovered how expensive the oxygen was - he eventually resorted to bringing stuff into school and using methane-compressed air in the hearth
I've had reasonable success at home (now retired) brazing up to 5/8 diameter and silver soldering up to 3/4" diameter steel tube for racks and bag supports using a (B&Q) GoSystem butane/propane torch at nominally 1450W. This needs several firebricks to reduce heat loss from the joint area, an excess of of flux due to the time involved, and much patience: 1/2" tube isn't a problem but larger diameters become increasingly marginal - I wouldn't attempt anything frame or fork related with it, but it's a useful addition to MIG + angle grinder (my welding is not neat - I don't practice enough)
I did an welding course organized by the LEA some decades ago to cover the H&S aspect for welding in school (3 of us welding as required, none of us had any formal training) - might be worth looking to see if this is an option - also ticks a few professional development / training boxes?
(just re-read / properly read the original post: 'teacher' is not the same as 'D&T teacher' so you might have to ignore the last bit...)