Opinions on Kumon??

Hi I started Kumon math for my going to be 1st grader and 3rd grader. I need some feedback from parents who have used or use this as a method for math enrichment. Here are my issues:
5 year old is going to 1st grade a very very young 6. He is academically on track and will turn 6 a couple of weeks before school starts. I started Kumon as a way for him to get a little summer enrichment and heads up before school starts. He gets a packet to do each day and the level is really low...addition by 1s. He can do it just fine but he is so bored by the repitition that he zones out and never makes the time requirement...he cries and whines and even sitting with him I cannto get him to complete the worksheet in under 10 mins. He does half a packet and then gives up and cries. Even at 20 mins he is crying and refusing to complete the work and saying he hates it. I am a little upset and needing feeback on this...Kumon is super boring and I am not sure what this particular level si supposed to achieve bc its adding by ones and requiring very little thought process but they will nto progress him any faster. He is also young so writing under timed conditions is hard for him and he is slow. This weekend he found a singapore math workbook from first grade....and old workbook we used at times with my older son to supplement class work and he worked trough many pages of it independently asking for help when he needed it. This workbook is pitched at kids in the latter part of first grade and conceptually he was understanding and wanting to do the work. I was worried after the kumon experience of daily crying over math sheets that he was somehow weak at math but this does not seem to be true. On the contrary my husband thinks DS has good number sense for a 5 year old which makes the "Enrichment" reason for doing Kumon that much more of a joke! I am wondering if any other families have tried Kumon and what they think...is it worth the money and the tantrums to stick it out at this level? My 3rd grader is doing better but he too is bored with the repitition and wanting to do something more challenging or interesting but that is not happening. Please give feedback?!! Thanks!