My dads saying my 125 4 stroke is better than an 85 2 stroke.

This is the answer you are looking for.
Ride the heck outta that 125 4 stroke, and enjoy every last second on it. Work on your fundamentals and really get to know how that thing works. Get to the point where you are riding it to its potential.

As you're doing this start blowing snow off driveways for people,ask your neighbors if they need work done, ask your parents if they need any work done that they'll pay you for. All this can be done right now, then with spring and summer around the corner youll have time off from school and plenty of other misc jobs you can do. By the end of summer I would bet my last dollar if you could find 3 days of work per week at 10$+ per hour you could buy your own 125. Then with that you have a bike that you really wont outgrow that is a two stroke ,and is more what you're looking for. If that doesn't work you can always do as Spudnut said and ask for Christmas. Remember keep good grades, keep the parents happy and I'm sure you'll get your way.

Just so you know about 125's. As a 29 year old dude I still ride my 125 and its one of my favorite bikes I own. You sound faster than you are which is my kinda speed.

Your dad may be thinking you will outgrow an 85 in a year and he doesn’t want to drop the cash on a bike that he will need to replace in a year with a full size bike. Shred on the bike you have. It will make you a better rider because you are the suspension.

Get some odd jobs pulling weeds for neighbors, find an old push mower (even a new one is less than $200) and mow a couple yards, paint fences, shovel snow, etc.

Not knowing your dad personally but that sounds like an answer I might give to my kids when either I do not have enough money, or I want them to show me their commitment and desire. I think the previous advice from many about doing what you can as far as working, showing your desire and riding what you have to your potential is spot on. You will have much improvement in basic skills that will benefit you down the road and help to keep you from developing lazy habits on the big bike because of its abilities. Also he might be tough to convince so do not give up. Just stay committed.

Growing up I wanted a bike more than anything else, but I could not convince my dad. I eventually bought one at 15 and trembled pushing it home thinking he would make me sell it. He never did. I think he saw my desire to work for it, and that he had no financial commitment and let me have what I wanted. Yes I did push it so that it would not be so hard if he made me sell it.

I remember when I was a kid I wanted a 125 really bad when I was on 85’s. I was 15 and my Dad wouldn’t get me one. I would have been to small for a 125 at 13. At 16 I aged out of the 80 class . I went down a path where I stayed in trouble and got sent to a reform school. I say if you can afford it, let your kids enjoy their passion. The only time I followed the straight and narrow was when I wanted to be in shape to race.
I would try to do chores or something to show him how much it means to you.

Your Dad is lying to you kid! Go get the 85, better yet, go pick up a super mini 105cc

When I was about your age I had an rm80 for the track and occasional racing. But for riding on the property up in the mountains, my dad got a Yamaha ttr-125 for my brother and I, which was a blast and not as much a nuisance for the neighbors sound-wise.

I still had a little too much respect, even some fear, of the 2-stroke powerband and didn't quite make it sing and squeal as it needs. But I learned to rail on that ttr on a turn track I made through the trees, and when I took it to the track I found I was faster on the ttr compared to the rm80 except for a few of the jumps I wouldn't attempt on it. Not to say it wouldn't have been capable, but I knew the landings would have been real rough and clanky.

I head Mike Alessi once had a crazy modified ttr-125 that he raced against 80s at some point, years before Honda came out with their 150r.

Remember in the other one where I and others mentioned that the way to go fast is to work on your skills?

Same applies here. Skills still transfer to whatever you have....skills are skills

Here is the part you'll really hate, because it's true, I bet there are a BUNCH of older fat guys who can go faster on your 150 than you can.

It's because they've worked on their skills. You can do braking skills on a scooter, doesn't need to be a 450.

It was mentioned earlier, work on your skills and when you'll crushing everyone and dragging bar around corners left and right, show your Dad what's up and then he'll think twice.

As for your age and jobs...BULLSHIT
Mow lawns, carry trash, clean the house, find things to work on and don't ask for anything and even volunteer at places. If you volunteer w/o pay, he'll see you're serious
Show some commitment. Show this isn't a whim and you're willing to work for it.