Magnus,
The only perfect sport specific activity for football is on the field playing football but we can come close in other ways. the weightroom is not the place to do most sport specific activities but some can be used even though they may not perfectly mimick the movement on the field. The olympic lifts are not the almighty of all exercises and neither is the jammer but they are damn good lifts to do. Dont get me wrong I love cleans and use them but they are just like anything else, an exercise. So I dont start any debates remember many lifts can be done explosively. The reason I say the jammer is more football specific than the clean is because of horizontal triple extension instead of vertical triple extension. No you will not find one on a football field and you wil not find a barbell either but we still lift weights. yes the jammer is extremely expensive but if your school wants to spend the money you can get very good use out of it. Read Coach H’s log at elitefts and get his opinion on it. Theres mine and I dont think it is either right or wrong just my opinion.