Hi, sorry to hear you are experiencing this. I am a primary school teacher in Y2 with a range of SEN experience. I am glad you have made an appointment, communication is the most important thing.
If you feel your LB is capable of more, I would ask a few questions:
How often are the IEP targets reviewed and measured? (This should be regularly and there may be smaller targets 'on the way' to these)
When was the last time they were reviewed?
What are his current levels and how far behind is he in terms of average (you should be looking at a 2b/2a for his age)?
It sounds like he has a good work ethic at home-is this replicated in school, where he has less 1:1 support in a different environment?
Doing column addition can be useful, however I have seen many children over the years who have learned this process, but have no concepts of what the numbers mean-or how large/small they are in comparison to one another...
I understand your concerns and the stigma sometimes attached with the lower set, but if you can meet the school in the middle, that would be a good approach-ask for more homework, but also for any websites or books they can recommend. The school will be grateful for your support but if the progress your LB isn't replicated in school, you may to work with his teachers to encourage independence and for him to show what he really knows, and is capable of.
When teamed with positive rewards and incentives, this sometimes has the biggest impact, especially as he is doing so well with his tutor.
I think your main aim is to see when he was last assessed and what his next steps are.
I hope this has helped and not been patronising in any way. Good luck!